In the Anthropocene, the.pdf

# Ecology in the Anthropocene ## Learning Objectives - Explain what the term ecology means, and describe what ecologists study. - Define the term Anthropocene. - Distinguish among the four approaches ecologists use in their science. - Differentiate between conceptual and mathematical models. - Expl...

# Ecology in the Anthropocene ## Learning Objectives - Explain what the term ecology means, and describe what ecologists study. - Define the term Anthropocene. - Distinguish among the four approaches ecologists use in their science. - Differentiate between conceptual and mathematical models. - Explain the scientific method and its iterative nature. ## 1.1 The Ecological "House" Ecology is a branch of biology that focuses on processes occurring between whole organisms and their environments. The term ecology derives from the German word *Oekologie*, meaning roughly the "doctrine of the household." This means ecology is the study of our "house" and the interactions within it. The "house" is the place where all the organisms live, including the air, water, soil, and rocks. An organism refers to a single individual of any type of living creature on the planet, including trees, birds, insects, worms, microbes, and all the other species that inhabit the Earth. A more complete definition of ecology is the study of the interactions that determine the distribution and abundance of organisms. These interactions can be: * among individuals that are members of the same species * among individuals of two or more species * among individuals and their physical environment In this context, an ecosystem can be defined as a group of interacting organisms and their physical environment. ## 1.2 Ecology in the Anthropocene Humans have heavily impacted the planet, and much like a house that has been battered by a bad storm, the Earth has ecological damage. The pervasive influence of people on the biosphere means that ecologists must use scientific principles and evidence to help ameliorate human effects and perhaps heal a rapidly changing Earth. In 2000, Eugene F. Stoermer and Paul J. Crutzen suggested that the pervasive planetary damage by humans warrants calling the current geological epoch the Anthropocene. An epoch is a subdivision of the geological timescale, and Crutzen and Stoermer were emphasizing the central role that humans play in the current era. An interdisciplinary group of scientists concluded in 2017 that "human impact has now grown to the point that it has changed the course of Earth history by at least many millennia, in terms of the anticipated long-term climate effects, and in terms of the extensive and ongoing transformation of the biota, including a geologically unprecedented phase of human-mediated species invasions, and by species extinctions which are accelerating". The Great Acceleration graphs show the sudden, intense increase across a range of planetary metrics due to human influence. These graphs show massive increases in human population and energy use, huge additions of carbon and methane into the atmosphere, a rise in air surface temperatures, the loss of tropical forests, and the global acidification and nitrification of the oceans. ## 1.3 What Do Ecologists Do? Ecologists have embraced a variety of approaches to understanding the complexity of the natural world: ### Observation and Natural History Early ecologists were called naturalists, or natural historians. These early scientists were skilled and patient observers of nature who inferred patterns and processes from their observations. The importance of careful observation remains the starting point for almost all ecological investigations. ### Experimental Ecology and Null Hypothesis Testing Beginning in the 1950s, ecologists increasingly began to approach their research through manipulative experiments and statistical hypothesis testing. This approach is focused on converting observations into falsifiable hypotheses, which requires scientists to identify specific mechanisms that influence an ecological system to avoid *ad hoc* fallacies. One of the key aspects of the experimental approach to ecology is its focus on converting observations into falsifiable hypotheses. This effort requires scientists to identify specific mechanisms that influence an ecological system and thus avoid *ad hoc* fallacies, sometimes referred to as "just-so stories." An *ad hoc* fallacy is a story or narrative that explains an observed pattern or process, and the "neat-ness" of the explanation or story is presented as evidence of the correctness of the explanation. For example, Rudyard Kipling published a series of amusing children's stories in 1902 with fanciful explanations for a variety of animal traits, such as explaining that elephants got their long trunks when a crocodile pulled on an elephant's nose. Kipling's explanations are entertaining but are fanciful leaps of imagination that make no attempt to support or falsify their claims. Scientists staunchly try to avoid this type of explanation. Instead, they look for evidence in the natural world and allow their "explanations" to change based on the evidence. Experiments provide a way to gather such evidence. When designing an ecological experiment, the goal is to alter or manipulate various key aspects, or *focal factors*, of an ecological system to see how the changes affect ecological outcomes or responses. This is what we mean by a *manipulative experiment*. The manipulated aspects are considered *treatments*, and researchers collect data on how the ecological system responds to the treatments. In general, scientists compare outcomes in systems with treatments to outcomes in systems serving as *controls*, in which the focal factors are not manipulated. ### Multiple Hypothesis Testing with Best-Fit Comparisons Scientists can collect quantitative observations of large-scale phenomena and use these data to understand an ecological process. This approach replaces a single falsifiable hypothesis (i.e., the null hypothesis) and alternative hypothesis with multiple more realistic (or alternative) hypotheses that "compete" with one another in their relative fit to the data. The set of competing hypotheses represents an informed understanding of how an ecological system works. ### Ecological Modeling Ecological modeling provides another way of exploring how various factors affect ecological dynamics without having to manipulate real ecosystems. Models are used in theory and practice by nearly all modern ecologists. Students learning ecology need familiarity with modeling for two important reasons: * Models are incredibly useful for understanding the mechanisms that produce ecological patterns and for predicting how complex ecological systems will respond to environmental factors. * Many fundamental tenets in the field are based on models, and understanding the logic that led to these principles requires understanding the models. There are two types of ecological models: * **Conceptual model:** A theoretical construct that puts various components in relationship to one another. It is a formalized idea about how things work. Conceptual models can track individuals as they grow from one developmental state to another, describe how resource pools change in response to season, or illustrate how species drift toward extinction via a series of linked forces. * **Mathematical model:** A version of a conceptual model that is solved or run on a computer in order to predict the model's performance. Mathematical models frequently involve simulations, or a series of functions represented by mathematical equations to connect the different components of a system. ## 1.4 How This Book is Organized - This book is structured to reflect how ecologists generally conduct their science: observations lead to ideas and conceptual models, observations and experiments yield data that allow ecologists to validate (or invalidate) those concepts, and analytical or simulation models (based on the conceptual model) explore and predict the behavior of the system being studied. - The book is organized into a series of chapters that explore the sub specialties of ecology: * **Ecology and Climate** * **Evolutionary Ecology** * **Physiological and Behavioral Ecology** * **Population Ecology** * **Community and Landscape Ecology** * **Spatial Ecology** * **Ecosystem Ecology** * **The Anthropocene: Human Impacts on Ecological Systems** ## Key Terms * *ad hoc* fallacy * alternative hypothesis * analytical model * Anthropocene * anthropogenic effect * conceptual model * control * data * ecology * ecosystem * extraneous factor * focal factor * hypothesis * hypothesis testing * manipulative experiment * mathematical model * naturalist * null hypothesis * organism * simulation model * treatment ## Conceptual Questions 1. Does the field of ecology differ from other biological fields with which you are familiar? In what ways is it similar to other fields? 2. General observation of the natural world was the main approach of early ecologists. Discuss how observation still plays an important role in modern studies. 3. Describe the scientific method as practiced by ecologists, as shown in Figure 1.15. 4. Generate a concrete ecological question, and show how you might use the scientific method as outlined in Figure 1.15 to determine an answer. 5. Compare and contrast the various ways that ecologists use the word model. In what ways is the word used in fairly conventional terms? What ways are new to you? ## Suggested Readings - Crutzen, P. J., and E. F. Stoermer. 2000. The “anthropocene.” Global Change Newsletter 41: 17–18. - Hilborn, R., and M. Mangel. 1997. The Ecological Detective: Confronting Models with Data. Monographs in Population Biology 28. Princeton, NJ: Princeton University Press. - Lubchenco, J. 1978. Plant species diversity in a marine intertidal community: Importance of herbivore food preference and algal competitive abilities. American Naturalist 112(983): 23–39. - Steffen, W., W. Broadgate, L. Deutsch, O. Gaffney, and C. Ludwig. 2015. The trajectory of the Anthropocene: The Great Acceleration. Anthropocene Review 2(1): 81–98.