Ecology

I. Introduction

The word “ecology” is derived from the Greek oikos, meaning “household” or “home,” and logia, meaning “study of” or “discourse,” as derived from logos, meaning “word,” “thought,” or “use of reason.” Ecology is a branch of science concerned with the use of reason to study the interrelationships between living things and their environments. It is a multi-disciplinary field focusing on the dynamics influencing the distribution and abundance of organisms in their respective habitats (cf. Wright and Boorse, 2017). In its broadest sense, it is the study of the structure and function of nature (cf. Odum, 1971). 

Ecology is a comprehensive, synthetic science that views natural systems as complex systems and studies them across a broad range of scales and hierarchies, from individuals to species, to populations, to communities, to ecosystems, to biomes (cf. Wright and Boorse, 2017, pp. 49-53). Ecological science addresses biotic interactions, but also the effects of abiotic or physical factors on the distribution of plants and animals at different scales. This includes the interactions of the lithosphere, the atmosphere, and the hydrosphere with the biosphere, along with the energy and matter fluxes across those boundaries. It encompasses the study of larger-scale biogeochemical cycling of water, carbon, nitrogen, phosphorus, and others. 

Some key sub-disciplines of ecology include: population ecology, landscape ecology, community ecology, ecosystem ecology, terrestrial ecology, aquatic ecology, microbial ecology, evolutionary ecology, physiological ecology, behavioral ecology, restoration ecology, human ecology, biogeography, conservation ecology, and systems ecology. This article begins with an historical account of the science of ecology, then considers philosophical and theological questions that have emerged from it, and ends with a summary of the Catholic response to those questions.

II. History of Ecology as a Scientific Discipline

As a formal science, ecology is relatively new. It first emerged in the nineteenth century, when Ernst Haeckel coined the term “ecology” in 1869. Following is an historical summary of the development of ecology, including its roots in ancient Greek and Roman thought. This is not an exhaustive history but is meant to show the general progression of human understanding of ecological relationships in the western world, leading to the emergence and growth of the named scientific discipline of ecology in the nineteenth and twentieth centuries. This “long look” at history is helpful because some historical patterns of thought have recurred and have implications for contemporary philosophical and theological understanding of ecological questions, or can provide a foundation for that understanding.

1. Pre-Christian studies of nature among the Greeks and Romans (400s BC – 1^st century AD). There are notable instances of serious studies of nature among certain Greek writers (cf. Morris, 2009, and Du Pisani, 2006). For example, Herodotus’ Histories in the 400s BC incorporated many wildlife observations about the ecology of animals, including examples of mutualism, predator-prey balances, and population ecology. In 380 BC, Plato recognized the environmental impacts of deforestation and subsequent erosion in the mountains of his home region of Attica. In the 300s BC, Aristotle developed an animal classification system, effectively distinguishing between vertebrates and invertebrates, as well as between mammals, birds, reptiles, amphibians, and fish. Aristotle also extensively explored the natures and causes of things. Aristotle’s pupil, Theophrastus, systematically classified plant life in a massive volume in ca. 300 BC. For the first century BC to the first century AD, a number of Greek and Roman writers commented on environmental degradation from human activities like farming, logging, and mining. 

2. Early Christian Era and the Patristic Fathers (1^st– 5^thcentury AD). The Greek Patristic Fathers in the first centuries of the Church developed the outlines of an early theology of creation. Within the context of Greek culture and philosophy, they integrated the lived reality of Christ’s life, death, and resurrection into a speculative theology that paid particular attention to the mystery of the Incarnation and its implications for Christian life and the understanding of God. This, in combination with the rise of Gnosticism and related heresies, led to an emphasis on the centrality and goodness of physical reality as createdand continually sustained by God the Creator. Moreover, Patristic theology emphasized the sacramental nature of reality, i.e., that physical realities can serve as an entrance point to spiritual realities. St. Augustine (354 – 430) engaged widely with philosophical and theological questions related to creation and the interpretation of the Book of Genesis. These Patristic themes are described in greater detail in Section IV of this article.

3. Emergence of the Early Religious Orders (6^th– 12^thcenturies). The sixth to twelfth centuries saw the emergence of the early religious orders such as the Benedictines and Cistercians. In the sixth century, St. Benedict of Nursia established Benedictine monasteries in which the monks engaged in agriculture as part of their spirituality and daily life. These expanded rapidly in the coming centuries, and cultivating the land became a central aspect of Benedictine spirituality. In the twelfth century, the Cistercians developed sustainable agriculture methods and experimented with restoring unused or abandoned parcels by converting them into fertile agricultural land.

Another milestone in this time period came from Arab scholarship. In the ninth century AD, Arab Muslim scholar Al-Jahiz became the first to describe the concept of the food chain. He also wrote about the effects of various environmental factors on animal survivorship.  

4. Medieval Approaches to Creation (13^th– 14^h centuries). In the medieval era, secular explorations of nature continued. For example, in the 1240s, Frederick II, emperor of the Roman Empire, published a detailed, illustrated six-volume work on The Art of Hunting with Birds, which contained many ecological observations. Some recognition of the potential negative impacts of human practices on the natural world emerged, such as the first air pollution control law in 1273, banning the use of “sea coal” in the city of London.

The early 13^th century saw the rise of universities, Scholastic philosophy, and the founding of the mendicant orders, most notably the Franciscans and Dominicans. These orders distinguished themselves with teachings and lived witness regarding the nature of creation and the role of humans within it. Notable among the Franciscans in this regard were St. Francis of Assisi (1181-1226), founder of the Franciscan order in 1209 and St. Bonaventure of Bagnoregio (1221-1274). Notable among the Dominicans were St. Albert the Great (~1200-1280), who can be considered a “Scholastic naturalist” (Edgerton, 2003), and his student, St. Thomas Aquinas. St. Albert the Great was named the patron saint of scientists in 1941 by Pope Pius XII. His student St. Thomas Aquinas (1225-1274) wrote extensively on theological questions pertaining to creation and the Creator. Franciscan and Dominican themes characterizing the medieval period are discussed in greater detail in Section IV of this article.

5. The Renaissance, Nature, and Science (14^th– 17^th centuries). The Renaissance planted the seeds of the Scientific Revolution, especially in early works of astronomy, botany, zoology, microbiology, entomology, and geology. During this period, there was a growing awareness of the interconnectedness of natural systems and human impacts on nature. The Renaissance was also marked by cultural advancements in literature, the arts, and architecture, and an appreciation of the beauty of natural landscapes. Leonardo da Vinci, Michelangelo, Rafael, Albrecht Dürer, René Descartes, Galileo, and Copernicus were active during the Renaissance. In 1503, the German artist, Albrecht Dürer, created the first work of art with an ecological theme, called “The Large Piece of Turf.”

Some pertinent historical markers for ecology during this period include Christopher Columbus’ return to Spain in 1493 from his voyage to the Americas, from which he brought many previously unknown plants, birds, and animals. He is also believed to be one of the first to note that forests have the effect of retaining and increasing rainfall. In 1556, Swiss naturalist Conrad Gesner completed his Historiae Animalium, a broad compilation of early vertebrate zoology. This was followed in 1583 by the first textbook of botany, produced by Italian scientist Andrea Cesalpino, entitled De Plantis Libri XVI. In ca.1590, the microscope was invented, and in 1603, the Lincean Academy was founded in Rome by Federico Cesi. In 1623, Gaspard Bauhin refined Cesalpino’s textbook and classified thousands of plants according to their genus and species names. One of the first known books on air pollution was published in 1661 by the Englishman John Evelyn. He suggested ways of improving the degraded air quality in London by burning wood rather than coal and moving dirtier industries away from the center, while replacing them with gardens and orchards. The 1660s – 1680s also saw early work in microbiology, entomology, and demography. 

In 1669, Danish scientist Nicholas Steno (1638-1686) discovered that tongue stones are actually animal fossils. He also formulated the laws of stratigraphy based upon his observations of rock formations in Italy (cf. Kermit, 2003, pp. 107-129). Because of this, Steno is considered to be the founder of modern stratigraphy. His groundbreaking work formed an important foundation for the development of the formal science of geology in the 17-19^th centuries, especially for the geologist James Hutton (1726-1797) and the geographer and naturalist Alexander von Humboldt (1769-1859). Steno’s laws are still taught in geology classrooms today. Steno was also a pioneering anatomist, who based his conclusions on careful observations and keen insight. His scientific studies of the body proved by experiment that the heart is not a furnace, as Descartes held, but a muscle that pumps. He also criticized Descartes’ claim that the pineal body in the brain is the link between the body and the soul. 

The insights from Steno’s work were significant from both scientific and theological perspectives. First, his work showed the value of an empirical method of experimentation that sought to uncover natural truths without fear of compromising philosophical or theological integrity. Second, his geological observations suggested that the earth’s history can be read in the layers of the earth. There is no indication that Steno questioned the age of the earth, as it was commonly held at that time that the earth was 6000 years old in accordance with the Scriptures. (The birth of geology pioneered by Steno, however, set the stage for later Enlightenment geologists, who drew upon their science to question the age of the earth.) Third, Steno is an excellent example of a “field scientist” whose practice of science did not conflict with his religious faith. He eventually converted to Catholicism from his native Lutheranism and was later ordained a Bishop. In a public lecture at the University of Copenhagen, Steno offered this striking statement of the harmonious relationship between science, reason, and faith: “That which we see is beautiful, that which we understand is even more beautiful, but the most beautiful of all is that which we cannot grasp” (Kermit, 2003, p. 60). 

6. The Scientific Revolution and the Enlightenment (17^th– 18^th centuries). The Scientific Revolution and the Enlightenment marked a major shift in western civilization, one that departed from Greek philosophical approaches and led to the prioritization of reason and science over philosophy and faith. The development of the experimental method and its successes led to a scientific enterprise increasingly convinced of the power of rationalism and empiricism and tending to be driven by utilitarian goals. A belief in the human powers of reason to accomplish continual, unlimited progress accompanied these developments.

Out of this, a new view of nature emerged – that of nature as a machine (cf. J. Mittelstrass, 1988). This was a departure from earlier views of nature as an organic reality. Nature was matter to be studied and controlled, like parts of a machine, by the rational human mind. As the mechanistic view of nature emerged and strengthened, tensions arose between it and more holistic/organic views of nature.

While ecology had not yet emerged as a formal scientific discipline, its “echoes” continued to resonate in natural history studies and grew more pronounced through certain important scientific developments. Antonie van Leeuwenhoek (1632 – 1723), the “Father of Microbiology,” discovered bacterial cells and described their interactions with their environment. He was also the first in the West to develop the concept of food chains (cf. Lane, 2015; Egerton, 2006). In his Systema Naturae, Carl Linnaeus (1707-1778), a leading naturalist, classified thousands of species, founding taxonomy and the system of binomial nomenclature for classifying plants and animals that is still in use today. He also invented an ecological approach married to a kind of natural theology that he called the “economy of nature,” which gives precedence to holistic and final-causal explanations of organisms in their environment. In his words: “By the Oeconomy of Nature we understand the all-wise disposition of the Creator in relation to natural things, by which they are fitted to produce general ends, and reciprocal uses” (Egerton, 2007). 

In 1749, French naturalist George-Louis Leclerc, Comte de Buffon (1707-1788), published 44 volumes of his Histoire naturelle, in which he defined the notion of species as groups of animals that can produce fertile offspring and considered the role of the environment in the distribution and diversity of species. In 1774, Joseph Priestley (1703-1804) published a treatise detailing his discovery of oxygen and his experiments demonstrating that plants convert the carbon dioxide breathed out by animals into oxygen. This laid the foundation for later understandings of photosynthesis. Research by Lavoisier and others explored the cycling of carbon and oxygen, as well as the role of nitrogen in the air and as a nutrient for plant growth. Also in this time period, mathematicians developed equations to describe and predict population growth. These were the precursors of the Euler-Lotka equations still in use today.

In 1795, Scottish founder of geology James Hutton (1726-1797) published his Theory of the Earth. His work was revolutionary in proposing the theory of uniformitarianism – that the earth’s landforms are the product of very long periods of uniform, gradual change. His work contradicted the prevailing Biblical worldview that the earth was 6000 years old, and that existing landforms were the product of the catastrophic Biblical flood. This had the effect of introducing apparent discrepancies between scientific and theological conceptions of the universe. Hutton’s work laid the foundations for evolutionary biology in the next century, as it painted the picture of a dynamic, continually developing earth rather than a static one.

In this time period, other tensions emerged between two rival schools of thought in the emerging field of ecology. “Arcadian ecology” had its roots in Renaissance appreciation of natural landscapes and was represented by the parson-naturalist Gilbert White in his Natural History and Antiquities of Selborne (1789). The goal of Arcadian ecology was a harmonious relationship between humans and nature in which humans live simply and humbly (Worster, 1994 and BioExplorer.net, 2023). Opposed to this was a contrasting school of thought known as “Imperial ecology,” which advocated for man’s dominance over nature through the exercise of reason and hard work (Worster, 1994). Scientists such as Descartes, Newton, and Francis Bacon were proponents of the imperial viewpoint. Imperial ecology promoted a utilitarian approach to nature as a commodity or resource, as well as a strongly anthropocentric view of humans as masters and dominators of the natural world (Oppermann, 2007). Arcadian ecology, on the other hand, emphasized the intrinsic goodness of nature, critiqued the reductionism and dualism of imperial ecology, and envisioned humans in a compatible, non-adversarial role in nature (VanKoppen, 2000). The opposing tensions between these two worldviews still exist in contemporary ecological discourse, as will be discussed further later in this article. 

7. The Industrial Revolution and the Emergence of Ecology (19^th century). The 19^th century saw the rise of the Industrial Revolution and the beginnings of the formal science of ecology. In its early stages, progress in the field of ecology was fueled by exploratory expeditions by the great maritime powers of the time, in which many field scientists participated. For example, the Prussian naturalist, Alexander von Humboldt (1769-1859), joined a five year long Spanish expedition to the New World, during which he catalogued thousands of species of plants and carried out many types of zoological, botanical, and geographical research. He organized his findings holistically within the context of the relationship between organisms and their environment. Because of this, he is considered by many scholars to be the Father of Ecology.

At the same time, the Industrial Revolution, driven by rapid scientific and technological progress, transformed primarily rural, agrarian societies into urban ones dominated by industrial development and mass production in factories (Allen, 2007). As cities and industries grew, so did pollution and disease. However, with the exception of George Perkins Marsh’s groundbreaking work, which is described below, it was not until the 20^th century that the science of ecology addressed the reality of pollution in a concerted manner. Another strain of thought with ecological implications that developed further in this period was mathematical work on population ecology.

The science of geology developed rapidly during this period. In 1830, the geologist Charles Lyell (1797-1875) published the first volume of The Principles of Geology in which he supported the principle of uniformitarianism formerly introduced by James Hutton. A decade later, Louis Agassiz presented his discovery of glaciation. These geological advancements provided evidence that diluvianism was not a valid explanation of landscape origins, thus reinforcing the perception of an apparent disjunct between scientific and theological explanations.

In 1859, influenced by Lyell’s geological notions of uniformitarianism, Darwin (1809-1882) envisioned of kind of biological uniformitarianism and proposed the theory of evolution in On the Origin of Species. Evolution describes descent with inherited modification, and Darwin’s contribution was to propose natural selection as a mechanism by which species adapt to their environments, with certain traits favoring the survival or selection of certain individuals. Darwin was also influenced by the work of the economist Thomas Malthus, An Essay on the Principle of Population (1798). Malthus asserted that overpopulation will occur if human populations are not kept in check by natural forces such as famine and disease, an idea that awakened in Darwin the notion that in nature only the best-adapted individuals survive in the struggle for existence. Darwin’s theory became the foundation for a new form of biology with ecological underpinnings, and it spurred further research on the adaptations of various species to their environments. 

Alfred Russell Wallace (1823-1913), a contemporary of Darwin, who had independently come to a similar theory of evolution, was the first to propose a “geography” of animal species. The central idea of his work was essentially ecological, that species are interconnected with one another and with their environments. Ernst Haeckel coined the term “ecology” in 1869, formally naming the science, and in 1875, Eduard Seuss defined the “biosphere” as holistic systems composed of living organisms and their environment. The notion that species exist in communities of living beings, or biocoenosis, was proposed by Möbius in 1877. In 1895, Eugene Warming inaugurated the discipline of biogeography, incorporating abiotic factors such as drought, fire, floods, etc. with biotic factors in the study of ecological communities. His university teaching on ecological plant geography and subsequent book, “Oecology of Plants,” significantly influenced ecological founders in the 20^th century, including Arthur Tansley, Henry Chandler Cowles and Frederic Clements (Biology Libre Texts, 2021).

Progress was made during this period in understanding the nature of cycles and human impacts upon them. For example, research in plant physiology progressed in its understanding of the nitrogen cycle. In 1824, Joseph Fourier described the greenhouse effect, and in 1872 Robert Angus Smith published Air and Rain: The Beginnings of a Chemical Climatology, in which he connected the discovery of acid rain with human activities (cf. Galloway, Leach, Bleeker and Erisman, 2013). Late in the nineteenth century, there was an emerging awareness of the phenomenon of invasive species and the possibilities of species extirpation (cf. Morris, 2009). 

In 1854, the American writer Henry David Thoreau published Walden Pond, or Life in the Woods in which he recounted his experience of living alone in the woods for two years and what it taught him about simple, humble living close to the land, apart from the “desperation” of industrialized society in the United States. Thoreau wrote from the Transcendentalist perspective, an American idealist movement with Romantic and Kantian underpinnings that arose in response to rationalism. Transcendentalists believe in the unity and divinity of nature, and value human goodness, creativity, and insight over materialist or overly rational approaches to the world.  

In 1864, five years after Darwin published On the Origin of Species, the American conservationist George Perkins Marsh (1801-1882) published his famous book, Man and Nature, or Physical Geography as Modified by Human Action. In it he warned of the dangers of abusing nature and of the impacts of destructive practices such as deforestation on erosion and watershed health. His book was groundbreaking in being the first published comprehensive analysis of human impacts on earth processes.

8. Rise of the Formal Science of Ecology and Ecological Movements (20^th and 21^st centuries). Ecological science expanded rapidly in the twentieth century. To the strands of geology and evolution that had influenced it in the 19^th century was added the new science of plate tectonics, originally proposed as “continental drift” by Alfred Wegener in 1912 and solidified as a grand theory of plate tectonics in the 1960s (Wright and Boorse, 2017, pp. 92-94). Plate tectonics was significant for ecological understanding because it allowed for the long periods of geographic isolation of populations needed for speciation and helped explain the global geographic distribution of plants and animals. These centuries also saw huge growth in the understanding of biogeochemical cycles, the combining of ecology with mathematics and mathematical modelling, applications to population ecology, conservation biology, and restoration ecology, and the development of ecological vocabulary such as niche, ecological succession, biodiversity, climate change, and resilience. As a science, ecology was marked not only by scientific discovery and experimentation, but also by a holistic focus on the interconnectedness between humans and nature, as well as on human impacts on ecological dynamics. The 20^th century saw the rise too of environmental movements ancillary to but dependent upon the verity of the ecological sciences, such as conservation associations, international environmental organizations, environmental literature, the growth of environmental curricula, and environmental law. 

Accompanying these movements were wide-ranging philosophical and religious responses associated with the political-social-ethical phenomenon of “environmentalism.” These, along with key scientific advancements in ecology during this time period, included:

• 1892: Sierra Club was founded by John Muir, a Scottish-American naturalist.
• 1901-1909: Theodore Roosevelt (1858-1919) served as president of the United States, creating the U.S. Forest Service (1905), and setting aside vast areas of public lands as national parks, wildlife refuges, and bird sanctuaries. His experiences as a cattle rancher exposed him to the problems of overgrazing and other land use-related issues.
• 1911: Botanist Henry Chandler Cowles published an article on “The Causes of Vegetational Cycles” in which he presented the notion of ecological succession. This work established Cowles as the founder of “dynamic ecology,” which dominated plant ecology for the first half of the 20^th century. This approach reinforced the image of nature as dynamic and in constant flux, over traditional images of fixed species and cycles.
• 1913: The British Ecological Society was founded, along with their Journal of Ecology, the first international, peer-reviewed ecology journal.
• 1914: The passenger pigeon went extinct, as the last known individual died in captivity in a Cincinnati zoo.
• 1915: The Ecological Society of America (ESA) was founded.
• 1917: Joseph Grinnell, an American ornithologist, established in a scientific paper the earliest notion of the “ecological niche” as the specific place and conditions within which a particular species can thrive.
• 1920: Ecology, the journal of the ESA, was founded.
• 1925-1926: Population ecology grew in prominence, notably with the Lotka-Volterra model of predator-prey interactions. The Lotka–Volterra equations are first order nonlinear differential equations that describe predator-prey population cycles.
• 1926: Russian scientist Vladimir Vernadsky published his book, The Biosphere, in which he defined the biosphere as the totality of all ecosystems, including their biotic and abiotic interactions, and acknowledged human impacts upon it. He pioneered the understanding of biogeochemical cycling.
• 1927: English zoologist Charles Sutherland Elton, commonly called the “father of animal ecology,” published Animal Ecology, in which he refined the definition of ecological niche and described trophic relationships. He is considered the founder of the terms “food chain” and “food cycles.”  
• ~1931–1938: The American Dust Bowl devastated farms in the midwestern United States. It was caused by a drought on top of over-plowed farmland, which, because the deep-rooted native prairie grasses had been removed for agriculture, caused massive erosion, dust storms, and crop failure. Farm families were forced to migrate, and the devastating effects of the Great Depression were intensified.  
• 1935: Arthur Tansley, a British ecologist, refined the term “ecosystem,” and ecology became the science of ecosystems. He defined an ecosystem as the assemblage of organisms in a given area and their interrelationships with biotic and abiotic factors in that area.
• 1935–1937: Frederic Clements studied plant succession and developed the idea of “climax communities” that develop in a linear process of succession to a predictable climax state. He extended this to the belief that ecological communities in themselves are organisms.   
• 1942: American ecologist Raymond Lindeman classified freshwater organisms according to feeding (trophic) levels and studied the energy flows between them, publishing this in his ground-breaking paper, “Trophic–Dynamic Aspect of Ecology.” 
• 1949: The naturalist Aldo Leopold published A Sand County Almanac, a compilation of essays in which he articulated his famous land ethic (Leopold, 1949, pp. 224-225). He championed the value of biodiversity and advocated practices of ecological restoration. 
• 1951: Victor Shelford pioneered food web and biome concepts (with Clements) and founded The Nature Conservancy. In 1958, he wrote a landmark book on the impact of biological invasions. With Arthur Tansley, he was active in formulating and implementing a British national policy on conservation.
• 1953: The ecologists Eugene and Howard Odum wrote the first ecology textbook, Fundamentals of Ecology, and ecology became a university course. 
• 1958–1959: G. Evelyn Hutchinson, considered to be the “father of modern ecology,” formulated and popularized a refined understanding of the concept of “niche.” He built upon Lindeman’s work and advanced the trophic-dynamic concept of ecosystems, raising ecology to a more rigorous science and formalizing its theoretical framework. 
• 1960s: The mathematical modelling of ecosystems advanced rapidly in this decade, along with the practice of long-term, large-scale ecosystem studies. One notable example was the Hubbard Brook experiment in the White Mountains National Forest in New Hampshire, USA. This was a landmark study, the first ever undertaken to study elemental flux and cycles on a long-term, watershed-wide basis. Acid rain was first discovered in the Hubbard Brook study, and important insights were gained regarding the ecological effects of clear-cutting and other human practices on the health of forests, streams, and lakes. In its wake, the Long-Term Ecological Research (LTER) program of the U.S. National Science Foundation and the International Biological Program (IBP) were established. 
• 1962: Rachel Carson published Silent Spring, detailing the harmful effects of pesticides like DDT on wildlife. The book was a bestseller that inspired the environmental movement in the United States. DDT was banned in the US in 1972.
• 1967: Lynn Townsend White Jr. published an influential article in the journal Science critiquing mainstream Christianity for the ecological crisis because of the Genesis mandate to “subdue the earth,” and proposing that St. Francis of Assisi be named the patron saint of ecology.
• 1968: Garrett Hardin published an article in Science called “The Tragedy of the Commons,” sparking conversations about pollution of commons like air, land, water, energy, and other non-renewable resources.  
• 1968: UNESCO hosted the Parish Biosphere Conference, which created the Man and Biosphere Programme.
• 1969: The Cuyahoga River in Ohio, USA, caught fire due to oil pollution, heightening public awareness of environmental pollution resulting from industrialization.
• April 22, 1970: The first Earth Day was held in the United States, and millions across the country gathered to support the growing grassroots environmental movement. By 1990, it had spread to more than 140 nations.
• Also in 1970, the U.S. Environmental Protection Agency was created and the Clean Air Act enacted, followed by the Clean Water Act in 1972, the Endangered Species Act in 1973, and the Safe Drinking Water Act of 1974. Many other environmental regulations and amendments followed.
• In 1972, the ecologist Robert MacArthur followed on Hutchinson’s work in theoretical ecology and, through his emphasis on hypothesis testing, helped to move ecology away from a descriptive science to a more rigorously experimental one. With E.O. Wilson, he is considered to be the father of island biogeography. His work drove the development of community ecology and landscape ecology.
• Also in 1972, the U.N. Conference on the Human Environment was held in Stockholm, Sweden, the first worldwide international environmental conference. Out of this the United Nations Environment Programme (UNEP) was founded. Also that year, the influential report, Limits to Growth, was published by the Club of Rome in which five factors (human population increase, agricultural production, nonrenewable resource depletion, industrial output, and pollution generation) were highlighted as causes of “the human predicament of mankind.” 
• In 1973, Canadian ecologist, C.S. Holling, published “Resilience and Stability of Ecological Systems,” initiating global interest in the phenomenon of ecosystem resilience. Resilience is the capacity of systems to maintain their essential structure and function in the face of disturbance or rapid, even catastrophic changes. His work gave birth to the international Resilience Alliance (https://www.resalliance.org/).
• The 1970s saw the birth of the “Gaia hypothesis” by chemist James Lovelock and microbiologist Lynn Margulis, named after the Greek Earth Goddess Gaia. 
• 1980s: A series of environmental disasters increased awareness of the harmful impacts of industrial chemicals and awakened international concern. These included: the Bhopal disaster at a Union Carbide Company plant in 1984, which killed thousands due to chemical exposure; the discovery of the ozone hole in Antarctica in 1985; the Chernobyl nuclear disaster in the Ukraine in 1986; and the Exxon Valdez spill of 11 million gallons of crude oil into Alaska’s Prince William Sound in 1989. The discovery of the ozone hole drove ratification of the Montreal Protocol on Substances that Deplete the Ozone Layer in 1989.
• In 1988, the volume Biodiversity, edited by E.O. Wilson, formalized the notion of biological diversity that had been developing since the 19^th century.
• Also in 1988, the Intergovernmental Panel on Climate Change (IPCC) was established to assess the risks of human-induced climate change. Their first report was issued in 1990, followed by subsequent reports in 1995, 2001, 2007, 2014, and 2022. The IPCC reports were increasingly definitive in attributing climate change to human activity and the increase of greenhouse gases in the atmosphere in the 20^th century.  
• 1992: The Earth Summit was held in Rio de Janeiro. The question of anthropogenic biodiversity loss was central to this summit and inspired the formation of the Convention on Biological Diversity (CBD).
• 1992: Epidemiologists Roy Anderson and Robert May published Infectious Diseases of Humans, which utilized mathematical models to study the spread of infectious diseases in populations. This inaugurated the field of ecological epidemiology. 
• 1997: Kyoto Protocol was adopted, to be effective in 2005. This committed industrialized countries to greenhouse gas reductions according to the United Nations Framework Convention on Climate Change. 
• 21^st century ecology: The emphasis has been on resilience, complex systems theory, ecological modelling, and the expansion of ecological science into applied research on sustainability (cf. Palmer, Bernhardt, et al., 2005). Research has grown in such areas as conservation, community, and landscape ecology, GIS analysis (geographic information systems), biodiversity, habitat fragmentation, climate change, ocean acidification, genetic diversity and phylogenetics, invasive species, and statistical meta-analysis (cf. Anderson, Elsen et al., 2021). The science of ecology has evolved from natural history and observational field studies to an increasingly data and model-driven science. Interdisciplinary collaboration and long-term, large-scale research has become firmly established. 
• The sub-field of restoration ecology also rose in prominence at the end of the twentieth century and into the twenty-first. Restoration ecology is the science underpinning the practice of ecological restoration, which seeks to repair degraded ecosystems and accelerate ecosystem recovery through practices such as revegetation, remediation, habitat enhancement, and/or species reintroduction or other forms of rewilding (cf. SER, 2004). The Society for Ecological Restoration was established in 1988, with its accompanying journals Ecological Restoration (est. 1981) and Restoration Ecology (est. 1993). In 2019, the United Nations adopted a resolution to proclaim 2021-2030 the UN Decade of Ecosystem Restoration. It began on World Environment Day, June 3, 2021. 
• Another trend in recent decades is increasing attention to the social dimensions of ecology and practices such as adaptive management that focus on improving resource management and decision-making through iterative learning combined with robust science (cf. Williams et al., 2009). Associated with this are movements away from science into more philosophical and theological questions revolving around the proper place of humans in nature and their responsibilities for alleviating environmental degradation. Some of the major philosophical-theological questions emerging from the science of ecology are addressed in the following sections.
   

III. Philosophical and Theological Questions Emerging from the Ecological Sciences

 As shown in the historical account, the science of ecology flows out of a long history of human interest in and engagement with the natural world, with a particular focus on the relationships between species and their environments and the patterns and causes of their geographies. Since the mid-twentieth century, ecological science has incorporated considerations of the impacts of human activity on natural resources and ecosystem dynamics. It is only natural then, that philosophical and/or theological questions regarding the proper role of humans in the natural world have arisen out of ecology. What has emerged in recent decades is that philosophical and theological questions are inseparable from ecological questions and further, that “[t]he real roots of the ecological crisis are ‘philosophical,’ as they emerge from a certain vision of the physical world and of humanity’s relationship with it” (Kureethadam, 2017, p.4).

Some of these philosophical or theological trends find their roots centuries ago with the Scientific Revolution and the radical separation of the scientific enterprise from natural philosophy. Others developed more recently in the environmental ethics of the twentieth century – spurred on, not only by the science of ecology, but also by the powerful influences of environmental advocates like Aldo Leopold, Rachel Carson, Lynn White, and Garrett Hardin, among others. In 1949, Aldo Leopold posited in his “Land Ethic” that the roots of the ecological crisis were essentially philosophical. Scientist Rachel Carson’s Silent Spring (1962), along with cultural events like Earth Day and a series of environmental disasters, accented the indispensable links between science and questions of stewardship. Dominating themes that arose through the 1960s and 1970s tended to pit the inherent value of nature against the worth of humans because of the negative impacts of humans on the environment. Lynn White’s influential article brought up perduring questions regarding the proper role of humans in nature and the role of religion and theology in reinforcing ecologically-damaging attitudes or worldviews. These strands of philosophical-theological thought were interwoven and at times in dissonance, resulting in conflicting views of the human-nature relationship. They are summarized below.  

1. The Rise of Science and the Distortion of the Human-Nature Relationship. As described previously, the Scientific Revolution and the Enlightenment initiated radical changes in natural philosophy, ways of knowing, and perceptions of the natural world. As the scientific enterprise developed, certain worldviews developed along with it. Thinkers like Francis Bacon and René Descartes were major figures in the transition away from the Aristotelian worldview and toward the modern scientific worldview. One key marker of this transition was the rejection of Aristotle’s philosophy of nature, with its conception of formal and final causes as intrinsic to the nature of things (cf. Savino & Hittinger, 2015; Savino, 2009). Rather, the emphasis throughout the scientific revolution was on the reduction of nature into its component parts in order to obtain knowledge of its material and efficient causes. This led to mechanistic conceptions of nature and an exaggerated sense of the power of human rationality, which tended to produce an ethos of mastery and domination and a dualist divide separating humanity from the rest of nature (cf. Kureethadam, 2017). In Descartes’ words: “Knowing the nature of behavior of fire, water, air, stars, the heavens, and all the other bodies which surround us. . . we can employ these entities for all the purposes for which they are suited, and so make ourselves masters and possessors of nature” (Nelson, 2002). 

The result is a kind of Gnostic approach to the world, grounded in a lack of trust and striving for control of the world through knowledge and power. For Bacon and Descartes, knowledge accords power, through deliberate experimentation by which scientists discover the efficient causes of things in order to be able to produce that effect at will (cf. Savino and Hittinger, 2015). While such mechanistic philosophies of science have the effect of producing grand conceptions of human capacities in relation to the natural world, they also shrink the nature of humans and creation and introduce dualisms that did not exist in ancient or medieval philosophies. Rather than looking at the beauty and intelligibility of creation with a sense of awe and wonder and perceiving in it a reflection of the Divine Creator, Enlightenment science, marked by Gnostic, Baconian, and Cartesian elements, sees the natural world as a field of activity whose potential is to be harnessed and controlled. A profound dualist divide emerged in which humanity, in a master-dominator role, is separated from the rest of nature, which is treated as inert matter to be utilized for human ends. 

2. Lynn White, Jr. and the Critique of Christianity: An Indictment of Anthropocentrism. Several hundred years later, with the dawning of ecological awareness in the mid-twentieth century, Lynn White, Jr. published a highly influential article in the prominent journal Science, entitled “The Historical Roots of Our Ecologic Crisis.” In this article, he proposed that the roots of the ecological crisis are more philosophical than technological or scientific, because: “What people do about their ecology depends on what they think about themselves in relation to things around them” (White, 1967, p. 1205). Whiteargued that the ecological crisis is an outgrowth of the worldview underlying technological advancement in the West and imputed blame for this worldview onto Christianity. “By destroying pagan animism, Christianity made it possible to exploit nature in a mood of indifference to the feelings of natural objects” (White, 1967, p. 1205). Because of the Genesis account, in which humans, made in the image and likeness of God, were called to till and dominate the earth, western Christianity “established a dualism of man and nature” and became “the most anthropocentric religion the world has seen” (White, 1967, p. 1205). Moreover, claims White, because of this extreme anthropocentrism, which promoted the mentality that “it is God’s will that man exploit nature for his proper ends,” Christianity bears a “huge burden of guilt” for the ecological crisis (White, 1967, p. 1205). What he proposed as a solution to the ecological crisis was not more science or technology, but a rethinking of the dualism of the man-nature relationship and ultimately “a new religion, or rethink our old one” (White, 1967, p. 1206). He then went on to laud St. Francis of Assisi as a humble corrective to extreme Christian anthropocentrism because he “deposed man from his monarchy over creation and set up a democracy of all God's creatures,” by naming them “Brother” and “Sister” (White, 1967, p. 1206). In a follow-up article entitled “Continuing the Conversation,” White proposed that the solution to resolving the man-nature dualism introduced by the anthropocentrism of Christianity was to “find a viable equivalent to animism” (White, 1973, p. 62).

White’s article was highly influential and has been read widely as a classic in the environmental literature. In response to his critique, along with reactions to the mechanistic approach of Enlightenment science, various forms of ecocentrism have arisen since the 1970s.

3. Ecocentrism in its Various Forms. Ecocentrism is an attempt to redress charges of anthropocentrism and bridge the man-nature dualism by according intrinsic value equally to nature and humans. Certain forms of ecocentrism also include a religious component that is seen as a corrective to the anthropocentrism of Christianity. The focus is on the intrinsic goodness of nature over its instrumental value, as well as on shifting emphasis away from the priority of humans to that of planet earth (cf. Washington, et al., 2017). Some of the biocentric philosophies arose in the romantic or transcendentalist movements of the 19^th and 20^th centuries as a counter to mechanistic Enlightenment philosophies. Writers such as Henry Thoreau and Rachel Carson, as well as those of more recent figures such as E.O. Wilson with his biophilia hypothesis (that humans have an innate love of and affinity for nature) and Robin Wall Kimmerer with her combining of indigenous wisdom and scientific knowledge, have been prominent proponents of ecocentric approaches. 

Aldo Leopold is generally considered to be the originator of the concept of ecocentrism, through his famous “land ethic,” which he encapsulated as: “A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise” (Leopold, 1949, pp. 224-225). Other primary tenets of his land ethic as he articulated them are: (1) Land, which includes soil, water, plants, and animals, is entitled to moral status; (2) “A land ethic changes the role of Homo sapiens from conqueror of the land community to plain member and citizen of it;” and (3) The human capacity for morality extends only to things we can concretely see, feel, understand, love, respect, and admire (Leopold, 1949, p. 204).  

Ecocentrism as he conceived of it focuses on the biotic community as a whole and on the holistic maintenance of ecosystem structure and function. Leopold was a proponent of the intrinsic value of wilderness and of the value of preservation over conservation (or wise use) of land. He co-founded the Wilderness Society with the goal that it be "one of the focal points of a new attitude—an intelligent humility toward Man's place in nature” (S.L. Flader, 1974, p. 29).  

Other forms of ecocentrism developed in the 1970s, most notably the Gaia hypothesis and Deep Ecology. Both of these are eco-philosophical approaches committed to opposing the man-nature dualism and replacing it with a holistic approach (cf. A. Scerri, 2016). Chemist James Lovelock and biologist Lynn Margulis proposed the Gaia hypothesis in 1972, naming it after the Greek goddess of the earth (cf. J. Lovelock, 1972; and J. Lovelock and L. Margulis, 1974). This theory posits that the earth operates as one superorganism, a complex, self-regulating system in which the biosphere drives change in the non-living physical and chemical conditions on earth so that the biotic and abiotic collectively co-evolve, in effect producing and maintaining the conditions necessary for life on earth. The biosphere is in constant interaction with the atmosphere, the hydrosphere, and the pedosphere, and the whole system is kept in a stable equilibrium through negative feedback loops. This holistic feedback system produces a kind of planetary homeostasis such as has been observed in phenomena like the global regulation of surface temperatures, ocean salinity, and oxygen levels in the atmosphere. The science of Gaia theory has been controversial, although it did influence the understanding of global warming. The theory has also been associated with neo-pagan religious outlooks. 

The Gaia hypothesis influenced the development of Deep Ecology. The main spokesman and founder of Deep Ecology was Arne Naess, who coined the term in a 1973 article (cf. A. Naess, 1973). Naess fundamentally rejected the man-in-environment image in favor of ecological egalitarianism and the value of diversity and cooperation in interconnected human-natural systems (cf. A. Naess, 1973). As it has developed over time, some key tenets of deep ecology are that: all beings have an equal right to life, irrespective of their value to humans; diversity is an essential value of living systems, and humans do not have the right to compromise this diversity except to satisfy essential human needs; substantially decreasing human population is essential to the flourishing of all life, since human interference has been so devastating to natural systems; and human attitudes and actions should be geared to appreciating the quality of life, not to an ever-increasing standard of living (cf. Devall and Sessions, 1985).

4. Pantheism and Ecology. Alongside ecocentric approaches, there have arisen over recent decades a variety of religiously-oriented approaches associated with ecology that are essentially pantheistic, i.e., asserting that God is identical with the cosmos, or that God is not distinct from or transcendent to the cosmos. These generally arise out of a deep love and reverence for the natural world that is expanded to equating the beauty and complexity of the world with God. Pantheistic approaches are sometimes embraced in approaching environmental questions because they seem to narrow the gap between humans and non-humans that arose in the Enlightenment and to heal or unify the dualistic relationship between them (cf. M.P. Levine, 1994). Because of this, pantheism, which existed in early Christian and pre-Christian times, has experienced a resurgence in recent decades. In ecological interpretations of pantheism, humans are part of nature, not above or distinct from other natural forms, and have evolved jointly alongside other creatures. The role of humans is to fulfill their evolutionary niche in the whole that is the earth.

5. Ecofeminism. Ecofeminism is another recent environmental philosophy, the term being coined by the French writer Françoise d’Eaubonne in her book, Le Féminisme ou la Mort (cf. d’Eaubonne, 1974). A primary tenet of ecofeminism is that there is a fundamental connection between the domination of nature and the oppression of women. Various strands of ecofeminism have been linked with Aldo Leopold’s land ethic and deep ecology. Like Leopold and deep ecologists, ecofeminists argue that how humans conceptualize wild and human nature has significant ethical consequences, and that non-human animals and even nature as a whole should have moral standing (cf. Primack and Cafaro, 2007; Warren, 2015). Further, they contend that many of contemporary society’s knowledge constructs are fundamentally dualistic, oppositional, and patriarchal. Ecofeminism has expanded and taken on varied forms, but underlying most of them is the drive to counter the dualisms of western industrial, capitalist societies that ecofeminists believe grew out of paradigms of mastery and dominance promoted by the Enlightenment and by patriarchal religions. Ecofeminists hold that these hierarchical, oppositional dualisms, such as male/female, nature/culture, and mind/body, are responsible for both the exploitation of nature and the suppression of women and other marginalized groups (cf. Mathews, 2017). They advocate for a feminist ethics characterized by relational values of care, empathy, and friendship that can bridge these dualisms and that should be exercised on behalf of natural and human communities, especially those that are most dominated or oppressed. 

6. Liberation Theology and Ecology. Liberation theology, a prominent strain of which arose through the work of Gustavo Gutiérrez, Leonardo Boff, and others in South America in the 1960s, has also in various settings extended itself to ecological questions. Liberation theology is a Christian response to poverty and social injustice that, like ecofeminism, advocates for the liberation of oppressed peoples, though the focus of liberation theology is more on poor and oppressed communities than on women. Liberation theology, with its “preferential option for the poor,” has at times broadened its concerns to the protection and freeing of creation, recognizing the interconnections between poverty and pollution and the fact that the poor suffer disproportionately from both. 

In certain contexts, such as in the work of Leonardo Boff, liberation theology (like ecofeminism) has advocated for engagement in political and cultural affairs in order to oppose what liberation theologians perceive as “the ethos of domination” evident in societal structures that oppress both the poor and the earth. Boff thus focused some of his political and social efforts not only on the liberation of the poor but of the entire earth, on which the survival of the poor and all creatures ultimately depend (cf. Furst, 2018). 

7. Process Theology. The reality of environmental degradation and accompanying debates over dualism and the human-nature relationship, along with the critique of anthropocentrism, inspired the development of the alternative philosophies addressed above. Another prominent response to these debates is process theology. Process theology is a school of thought grounded in the metaphysics of the English mathematician-philosopher Alfred North Whitehead (1862-1947) and his American student Charles Hartshorne (1897-2000). John Cobb (1925- present) has also been a prominent spokesman. Whitehead’s 1929 book entitled Process and Reality: An Essay in Cosmology is considered to be the foundational document for this approach, although the term “process theology” did not come into common use until the 1950s (J. Cobb, Jr.). Process theology developed in an effort to counter the dualism of mechanistic philosophies with a conception of an immanent God rooted in and affected by the world around us, and to reconceive the human-nature relationship in a less anthropocentric way. 

The God of process theology is not identical to the world as in pantheism but is both in the created world and beyond or outside it, in a relationship called panentheism. Thus, the process God is not completely eternal, unchangeable, and immutable as in classical theism, though he is in some respects, but in other respects he is temporal, changeable, and mutable (cf. D. Viney, 2022). God as creator is distinct from his creation, while at the same time he is changeable because he is in a relationship of cooperation with a dynamic and changing creation. He is connected to creation and affected by it; he is capable of changing with, or as a result of, his connectedness with the created world. God is in a kind of “give-and-take” relationship with the world and with human persons (D. Viney, 2022). 

Process theology emphasizes process and becoming over substance, and experience or events over reality. Substances as independent entities do not exist in process thought; rather, creation is a series of events and of patterns of change and becoming. Process theologians see their approach as a corrective to what they consider dualism in both science and Christianity – i.e., the excesses in science that have led to scientific materialism, and the “supernaturalism” of Christianity that has kept God in a realm separate from the world (J.T. Howe, 2009). As process theologian Thomas Howe states: “Process theology offers amendments and corrections to both of these sides and provides a naturalistic theism that can provide for a relationship of mutuality between science and theology” (J.T. Howe, 2009, p. 961).

As to the nature of the created world and of humans, process theologians reject the Cartesian notion of nature as a purposeless machine, contending that subjective experience of the world, as well as the data of the ecological sciences, should teach us that nature is more than just mechanical matter. Process theologians emphasize the mutual interdependence between humans and all living things and reject what they see as Christianity’s highly anthropocentric approach. Rather, they argue that from the experience of interconnectedness – again, augmented by the ecological sciences – the nature of humans as “persons-in-community” emerges. John Cobb explains what is meant by this explanation of human persons according to the process theology perspective (J. Cobb, Jr.):

Although the community is constitutive of personal being, it is equally true that personal being is constitutive of community. People are neither isolated individuals nor mere parts of a greater whole. They are persons-in-community. The community of which they are a part is not only the human one. The human community is part of a larger society of living things, of an ecosphere, and even of the total biosphere. The wellbeing of the human community and of the persons who make it up is inseparable from the wellbeing of the whole. This is far closer to dominant Biblical ways of thinking than the alternatives.            

IV. The Catholic Response: Catholic Teachings on Ecology

The preceding sections show that the historical development of ecology and the philosophical\theological questions emerging from it coalesce around a number of key questions or areas of concern. First, certain dualistic tendencies resurface throughout history, producing tensions between opposing approaches often pitted against one another in the progression of science and religion. Some key examples of these tensions or dualisms as described in previous sections include: (1) material vs. formal or final cause, (2) reductionism vs. holism, (3) anthropocentrism vs. ecocentrism, and (4) pantheism or panentheism vs. theism. The science of ecology occupies a unique place in relation to these dualisms. As a naturally holistic, interdisciplinary science, ecology has not suffered as much from reductionism, mechanism, and materialism (tensions 1 and 2) as have other scientific disciplines. In approaching the natural world as a complex, interconnected system, ecology has naturally focused on the formal causes of things as they are wholes operating within wholes. Indeed, many of ecology’s founders believed it to be a scientific corrective for the mechanistic, reductionist approach to science that emerged in the Enlightenment and expanded through the Industrial Revolution. Ecology has been effective in bridging the first two dualistic tensions and demonstrating that the scientific enterprise does not have to be mechanistic and reductionistic. 

Yet significant tensions have also arisen in ecology, especially in relation to dualisms 3 and 4. While materialist, reductionist approaches push the boundaries between science and religion by enlarging the scientific enterprise and “shrinking God,” so to speak, the holistic drive in ecology has in certain circumstances blurred the boundaries between science and religion by subsuming them into a kind of cosmic pantheism. In this conception, nature and God become equated with one another, and human uniqueness is downplayed. Underlying these tensions is the core question of the nature of the human person and of creation. This has been a matter of debate since the early centuries of the Church in its encounter with Greek and Roman pagan philosophies. It resurfaced prominently in the Enlightenment with the rise of the Cartesian paradigm, and it intensified in the mid-twentieth century with the counter-responses of the ecological movement. Key Catholic responses to these areas of concern are addressed in the following sections.

1. Patristic Understandings of Creation. From the early centuries of the Church, the Patristic fathers argued against various sorts of dualisms such as Gnosticism and Manicheism. They developed an early theology of creation, grounded in the notion that contemplation of nature is a spiritual process, in that contemplating the “logoi” of created things is a pathway to the divine Logos (cf. Juurikkala, 2020). In formulating foundational doctrines of the Incarnation and the Trinity, they upheld the unity of certain teachings about the nature of the Creature and the created world. These included the doctrines of: creation ex nihilo, the transcendence and immanence of God in creation, the goodness of creation, the absolute dependence of the created world upon the Creator, and the relation of love between Creator and created. These teachings have provided a “benchmark” for Catholic teachings on creation (cf. Dembski et al., 2008). They naturally counter the four dualist tensions highlighted above by presenting a God who is both transcendent and immanent to his Creation because of his incarnation and his Trinitarian nature. He created nature out of love and is in a continuing relationship of love with his creatures. Athenagoras, Irenaeus, Athanasius, and other Patristic fathers used the image of the universe as a well-tuned instrument played and tuned by God (cf. Dembski et al., 2008, pp. 23-25, 28,195). They emphasized that Christians distinguish God from matter, not conflate the two as pagans or pantheists do, and that the beauty of creation should lead to worship of the “Artificer” who created the world, not to worship of the world itself. Irenaeus frames it this way – that creation reveals the God who created it, so that physical realities in their integrity of form continually point beyond themselves, from the secondary to the primary (Irenaeus): 

He [God] kept calling them to what was primary by means of what was secondary, that is, through the foreshadowings to the reality, through things of time to things of eternity, through things of the flesh to things of the Spirit, through earthly things to the heavenly things.

About the place of humans in this creation, Ireneaus, like the other Patristic fathers, holds an anthropocentric view, but not one that envisions humans as masters or dominators. His famous quote – “The glory of God is the human being fully alive!” – is grounded in the conviction that the Incarnation of God as a human being elevated the human state and accorded it a particular dignity. However elevated they may be, though, humans are created; they are not God. The Patristic Fathers would not envision the mechanistic, reductionist universe of the Enlightenment with its exalted conception of the powerful individual human being. Neither would they envision a pantheistic or panentheistic universe, because even though the Creator and the creation were inextricably linked, they possess distinct natures that could never be mixed.  

St. Basil the Great in his Hexaemeron, or treatise on the six days of creation in Genesis, reinforced these teachings, emphasizing that God created the world ex nihilo and that study of the world should lead persons to the Creator whose power, wisdom, and goodness shine forth in his creation. St. Augustine, in his Literal Meaning of Genesis, emphasized the reverence that is due to created things, due to their intrinsic goodness as created and to the fact that they give glory to God. They give glory to the Creator, both in themselves and by virtue of the reality that they are part of a whole, ordered universe (cf. George, 2022). His approach also reflected an interest in explorations of the natural world, grounded in the conviction that the truths of nature cannot contradict the truths of the faith, since there is one Truth. St. Augustine’s theology of creation stood against the gnostic dualism of Manicheism to which he was an adherent before his conversion to Christianity. 

2. Medieval Understandings of Creation. Representative thinkers in Catholic medieval understandings of creation include the great Franciscan saints St. Francis of Assisi and St. Bonaventure, along with their Dominican counterparts, St. Albert the Great and St. Thomas Aquinas. St. Francis is known for his close and unique relationships with creation, as manifested especially in his famous Canticle of the Creatures. In the Canticle, St. Francis sings the praises of creation, especially its fraternal interrelatedness as “Brother Sun” and “Sister Moon,” and rejoices in how God is praised through His creatures. He was named the patron saint of ecologists centuries later in 1979 by Pope John Paul II and was invoked in a particular way by Pope Francis in his 2015 environmental encyclical Laudato si’, which is named after the opening words of St. Francis’ Canticle. 

Seeking to put into words what St. Francis of Assisi lived, St. Bonaventure of Bagnoregio wrote his Itinerarium Mentis in Deum, or Spiritual Journey of the Soul to God in 1259. In this spiritual document, the spiritual journey is envisioned as a pilgrimage from the exterior world and the senses, to the interior world of human understanding and will, and finally, progressing in an ascending movement to the transcendent, Trinitarian God. In essence, the person attains union with God through relationships with His creation. It is through the physical creation that one progresses to the spiritual. There is no dualism between the material and the spiritual because the transcendent God is accessible through his creation; He is both transcendent and immanent to His creation. 

St. Bonaventure in his Commentary on the Sentences of Peter Lombard advanced the image of the human person as a mediator between the created world and God. This middle position is unique in all creation and entails being between two extremes, sharing the properties of each. The mission of the mediator is to be “in the middle” between non-human creation and the Creator and to be a bridge between them (Savino, 2008, p. 72). Humans are therefore both part of, and yet distinct from, the rest of creation (Savino, 2009). Created in the image and likeness of God, they are to follow in the footsteps of Christ, the Prime Mediator. Bonaventure does have an anthropocentric perspective in asserting that humans are called to exercise authority over the created world according to the Genesis mandate; however, he does not understand this as giving humanity license to exploit and subjugate creation. “In Bonaventure’s thought, creation is only subject to humanity when humanity is subject to God” (Savino, 2008, p. 85).

St. Albert the Great (~1200-1280) was notable among the early Dominicans for his scientific and theological pursuits. Pope Pius XII named him the patron saint of scientists in 1941. Drawing upon Aristotelian sources, St. Albert embraced Aristotelian causality, and his work in wide-ranging classifications of plants, animals, and minerals, alongside theology, was a witness to the study of nature as a legitimate science and to the unity of material, efficient, formal and final causes. Even as he studied the individual species or aspects of the created world, he never divorced them from their existence within a whole creation created and sustained by the Creator.  

St. Thomas Aquinas, the student of St. Albert, treated the question of creation and the Creator from a theological perspective. Like his mentor, St. Thomas embraced the Aristotelian framework of causality. In his Commentary on the Sentences, he emphasized the unity of the Creator – that God is one – and that creation is a theological term referring to the conferral of being to things and their continual sustaining into being (Baldner and Carroll, 1997, pp 74-76). Because creation is a conferral of being by the first cause, creatures have a certain relation to the Creator as a principle of their being, even as they are distinct from the Creator. There is no confusion between Creator and created, nor between humans as created and the rest of the non-human creation. Further, the fundamental natures of things are a unity because of the Divine principle within them, and those fundamental natures cannot be manipulated, amalgamated, or destroyed.

These theological insights resolve the dualistic tensions mentioned above, countering reductionism, materialism, and pantheism or panentheism, as well as articulating and distinguishing between the natures of God, humans, and the non-human creation. In addition, out of these fundamental concepts about the nature of God and creation developed the principle of sacramentality. This principle, grounded in the teaching that matter points beyond itself to its Creator, is essential to resolving dualist tensions and fundamental for articulating Catholic approaches to ecology.

3. Magisterial Teachings on Creation and Ecology in the 20^th and 21^st centuries. The historical tradition of Catholic Christianity emphasizes creation as an act of God and humans as distinct in the created world. Lynn White indicted Christianity for what he interpreted as an overly anthropocentric stance. On the other hand, some contemporary environmental movements have absolutized nature in their desire to safeguard it and have deemphasized human uniqueness. What is the contemporary Catholic response? 

Since the rise of the ecological sciences, the Church has taken ecological questions seriously, as attested to by numerous statements by recent Popes and Bishops’ conferences from around the world, beginning in the 1970s (cf. Christiansen, and Grazer, 1996). Since 1968, the Pontifical Academy of Sciences has also hosted a number of conferences focused on environmental or sustainability-related themes (cf. Tatay-Nieto, 2020). As for papal statements regarding ecological questions, these have increased in frequency and urgency since Vatican II. The following highlights some of the key papal statements and teachings regarding creation and the responsibility of humans for its care.

In 1971, Pope Paul VI in Octagesima Adveniens wrote that: “Man is suddenly becoming aware that by an ill-considered exploitation of nature he risks destroying it and becoming in his turn the victim of this degradation.” In a theme that will recur with later popes, he recognizes the connections between degradation of the “material environment” and the “human framework” (no. 21). 

The interconnectedness of natural and human ecology and the bearing of this on morality has become a central theme in Catholic teachings on ecology. In Centesimus Annus (1991) and his World Day of Peace message in 1990, entitled “Peace with God the Creator, Peace with all Creation,” Pope John Paul II referred to the need for a moral response to the ecological crisis, grounded in an authentic human ecology.  

Although people are rightly worried—though much less than they should be—about preserving the natural habitats of the various animal species threatened with extinction, because they realize that each of these species makes its particular contribution to the balance of nature in general, too little effort is made to safeguard the moral conditions for an authentic “human ecology.” Not only has God given the earth to man, who must use it with respect for the original good purpose for which it was given to him, but man too is God’s gift to man. A person must therefore respect the natural and moral structure with which he has been endowed. (Centesimus Annus, no. 38) 

His successor, Pope Benedict XVI, repeatedly addressed ecological questions, especially in his encyclical Caritas in veritate in 2009 and his World Day of Peace message in 2010. Two key themes in his pontificate were the importance of learning to read the “grammar of creation,” “which sets for ends and criteria for its wise use” (Caritas in veritate, no. 48), and the mutuality of natural and human ecology, that “[t]he way humanity treats the environment influences the way it treats itself, and vice versa” (no. 51). Nature, he wrote, “expresses a design of love and truth”and “speaks to us of the Creator and his love for humanity.” It is “destined to be ‘recapitulated’ in Christ at the end of time” and is therefore a special “vocation” for human beings, who are unique in being “constituted not only by matter but also by spirit, and as such, endowed with transcendent meaning and aspirations” (no. 48). 

Benedict XVI warned of the temptation of getting caught in the opposingextremes of either a “new pantheism” that views nature as more important than humans, or a stance of technical domination that views nature as “raw material to be manipulated at our pleasure” (no. 48). He expressed concern about the lack of respect for life inherent in both extremes.In his World Day of Peace message, he identified the master-dominator paradigm as one factor responsible for the ecological crisis because “man . . . sets himself up in place of God,” and “ends up provoking a rebellion on the part of nature” (no. 6). This extreme can tend to prioritize human ecology over natural ecology, while the pantheistic extreme tends to prioritize natural over human ecology. To counter these extremes, Pope Benedict called upon humans to assume their special role as “God’s co-workers.” 

In terms of the anthropocentrism vs. ecocentrism question, the Catholic approach is anthropocentric and involves a certain prioritization of human ecology, though with the understanding that this does not equate to a master-dominator role. In fact, the master-dominator role has at times extended to practices that harm human ecology in profound ways, as Pope Benedict indicated in Caritas in Veritate (no. 51): 

If there is a lack of respect for the right to life and to a natural death, if human conception, gestation and birth are made artificial, if human embryos are sacrificed to research, the conscience of society ends up losing the concept of human ecology and along with it, that of environmental ecology.

Because they are interconnected, lack of respect for human ecology will lead to lack of respect for natural ecology. This is one reason why the Catholic Church has expressed moral opposition to population control as a strategy for reducing environmental impacts. Resolving tensions between human and natural ecology – while holding to a fundamental respect for human life without compromising the intrinsic goodness of all creation – can be complex in practice and is a key question for the ongoing science-religion dialogue in relation to ecology. 

Pope Francis, with his 2015 encyclical Laudato si’, gave worldwide prominence to the ecological question. He situated the encyclical in continuity with his predecessor popes and with the Church’s social teachings. He stressed that caring for creation and “protecting God’s handiwork” is a “vocation, . . . essential to a life of virtue; it is not an optional or a secondary aspect of our Christian experience” (Laudato si’, no. 217). Like John Paul II and Benedict XVI, Pope Francis called Christians to an “ecological conversion, whereby the effects of their encounter with Jesus Christ become evident in their relationship with the world around them” (no. 217). Quoting Benedict XVI: “The external deserts in the world are growing, because the internal deserts have become so vast,” he emphasized the interconnectedness of natural and human ecology and proposed “integral ecology” as the Catholic Church’s answer to the ecological crisis. 

According to the encyclical, integral ecology is a marriage of natural and human ecology and includes environmental, economic, social, and cultural ecology, the ecology of daily life, the principle of the common good, and intergenerational solidarity (no.137-162). Like his predecessors, Pope Francis is critical of what he calls the “schizophrenia” in contemporary ecological dialogue, “wherein a technocracy which sees no intrinsic value in lesser beings coexists with the other extreme, which sees no special value in human beings” (no.118). His response is to reaffirm the unique role of humans as in a middle position between misguided anthropocentrism and biocentrism (no.118):

[O]ne cannot prescind from humanity. There can be no renewal of our relationship with nature without a renewal of humanity itself. There can be no ecology without an adequate anthropology. When the human person is considered as simply one being among others, the product of chance or physical determinism, then “our overall sense of responsibility wanes.” A misguided anthropocentrism need not necessarily yield to “biocentrism,” for that would entail adding yet another imbalance, failing to solve present problems and adding new ones. Human beings cannot be expected to feel responsibility for the world unless, at the same time, their unique capacities of knowledge, will, freedom and responsibility are recognized and valued.

Pope Francis invoked St. Francis of Assisi as the exemplar of “an integral ecology lived out joyfully and authentically” (no.10). In this he is in agreement with Lynn White, but not for the same reasons. In the second chapter of Laudato si’, Pope Francis addresses the question of Biblical interpretations of the Genesis account and clarifies the Church’s teaching in this regard, reaffirming “a relationship of mutual responsibility between humans and nature” (no.67): 

We are not God. The earth was here before us and it has been given to us. This allows us to respond to the charge that Judaeo-Christian thinking, on the basis of the Genesis account which grants man “dominion” over the earth (cf. Gen 1:28), has encouraged the unbridled exploitation of nature by painting him as domineering and destructive by nature. This is not a correct interpretation of the Bible as understood by the Church. Although it is true that we Christians have at times incorrectly interpreted the Scriptures, nowadays we must forcefully reject the notion that our being created in God’s image and given dominion over the earth justifies absolute domination over other creatures. The biblical texts are to be read in their context, with an appropriate hermeneutic, recognizing that they tell us to “till and keep” the garden of the world (cf. Gn 2:15). “Tilling” refers to cultivating, ploughing or working, while “keeping” means caring, protecting, overseeing and preserving. This implies a relationship of mutual responsibility between human beings and nature.

V. Future Trajectories for the Ecology-Theology Dialogue

Since the mid-twentieth century, the Catholic Church has articulated a coherent response to the ecological crisis and to the various philosophical and theological tensions that have arisen out of it. With Pope Francis’ latest encyclical, Laudato si’, it has prioritized these concerns and articulated a framework of integral ecology that proposes a mutual relationship between natural and human ecology, with the unique human capacities of knowledge, will, freedom, and responsibility being essential and irreducible components of human ecology. Tensions still exist around how to facilitate and foster this mutual relationship. This is fodder for future dialogue between ecology and theology. One opportunity in this regard is to introduce new images of the human person that provide alternatives to both the master-dominator and the biocentric images. 

In the sixth and final chapter of Laudato si’, Pope Francis calls for new forms of ecological education according to the integrated principles elucidated in the encyclical. This will necessarily require robust dialogue between the science of ecology and the theology of creation – another area for future work. 

Finally, the science of ecology and its intersection with human ecology has many applications in terms of contributing to local and global human development goals. It will be important to develop strategies that both preserve human dignity and recognize the intrinsic goodness of creation in order to meet human development goals and ensure the sustainability of ecological systems for future generations.