An ecosystem consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and microbes.
Human ecology is an interdisciplinary and transdisciplinary study of the relationship between humans and their natural, social, and built environments. The philosophy and study of human ecology has a diffuse history with advancements in ecology, geography, sociology, psychology, anthropology, zoology, epidemiology, public health, and home economics, among others.
Agroecology is an academic discipline that studies ecological processes applied to agricultural production systems. Bringing ecological principles to bear can suggest new management approaches in agroecosystems. The term can refer to a science, a movement, or an agricultural practice. Agroecologists study a variety of agroecosystems. The field of agroecology is not associated with any one particular method of farming, whether it be organic, regenerative, integrated, or industrial, intensive or extensive, although some use the name specifically for alternative agriculture.
Urban ecology is the scientific study of the relation of living organisms with each other and their surroundings in an urban environment. An urban environment refers to environments dominated by high-density residential and commercial buildings, paved surfaces, and other urban-related factors that create a unique landscape. The goal of urban ecology is to achieve a balance between human culture and the natural environment.
Habitat conservation is a management practice that seeks to conserve, protect and restore habitats and prevent species extinction, fragmentation or reduction in range. It is a priority of many groups that cannot be easily characterized in terms of any one ideology.
An ecological or environmental crises occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. These ecosystems, functioning in healthy relationships, offer such things as natural pollination of crops, clean air, extreme weather mitigation, and human mental and physical well-being. Collectively, these benefits are becoming known as ecosystem services, and are often integral to the provision of food, the provisioning of clean drinking water, the decomposition of wastes, and the resilience and productivity of food ecosystems.
Ethnoecology is the scientific study of how different groups of people living in different locations understand the ecosystems around them, and their relationships with surrounding environments.
Health ecology is an emerging field that studies the impact of ecosystems on human health. It examines alterations in the biological, physical, social, and economic environments to understand how these changes affect mental and physical human health. Health ecology focuses on a transdisciplinary approach to understanding all the factors which influence an individual's physiological, social, and emotional well-being.
Ecological indicators are used to communicate information about ecosystems and the impact human activity has on ecosystems to groups such as the public or government policy makers. Ecosystems are complex and ecological indicators can help describe them in simpler terms that can be understood and used by non-scientists to make management decisions. For example, the number of different beetle taxa found in a field can be used as an indicator of biodiversity.
Biological integrity is associated with how "pristine" an environment is and its function relative to the potential or original state of an ecosystem before human alterations were imposed. Biological integrity is built on the assumption that a decline in the values of an ecosystem's functions are primarily caused by human activity or alterations. The more an environment and its original processes are altered, the less biological integrity it holds for the community as a whole. If these processes were to change over time naturally, without human influence, the integrity of the ecosystem would remain intact. The integrity of the ecosystem relies heavily on the processes that occur within it because those determine what organisms can inhabit an area and the complexities of their interactions. Most of the applications of the notion of biological integrity have addressed aquatic environments, but there have been efforts to apply the concept to terrestrial environments. Determining the pristine condition of the ecosystem is in theory scientifically derived, but deciding which of the many possible states or conditions of an ecosystem is the appropriate or desirable goal is a political or policy decision and is typically the focus of policy and political disagreements. Ecosystem health is a related concept but differs from biological integrity in that the "desired condition" of the ecosystem or environment is explicitly based on the values or priorities of society.
The following outline is provided as an overview of and topical guide to ecology:
James J. Kay was an ecological scientist and policy-maker. He was a respected physicist best known for his theoretical work on complexity and thermodynamics.
In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorms, insect population explosions, and human activities such as deforestation, fracking of the ground for oil extraction, pesticide sprayed in soil, and the introduction of exotic plant or animal species. Disturbances of sufficient magnitude or duration can profoundly affect an ecosystem and may force an ecosystem to reach a threshold beyond which a different regime of processes and structures predominates. When such thresholds are associated with a critical or bifurcation point, these regime shifts may also be referred to as critical transitions.
Regenerative design is an approach to designing systems or solutions that aims to work with or mimic natural ecosystem processes for returning energy from less usable to more usable forms. Regenerative design uses whole systems thinking to create resilient and equitable systems that integrate the needs of society with the integrity of nature. Regenerative design is an active topic of discussion in engineering, landscape design, food systems, and community development.
Sustainability is a social goal about the ability of people to co-exist on Earth over a long time. Specific definitions of this term are difficult to agree on. They have varied with literature, context, and time. Experts often describe sustainability as having three dimensions. These are environmental, economic, and social. Many publications state that the environmental dimension is the most important. So in everyday use, sustainability often focuses on countering major environmental problems. These include climate change and loss of biodiversity. They also include loss of ecosystem services, land degradation, and air and water pollution. The idea of sustainability can guide decisions at the global, national, and individual levels. A related concept is sustainable development, and the terms are often used to mean the same thing. UNESCO distinguishes the two like this: "Sustainability is often thought of as a long-term goal, while sustainable development refers to the many processes and pathways to achieve it."
Ecosystem management is an approach to natural resource management that aims to ensure the long-term sustainability and persistence of an ecosystems function and services while meeting socioeconomic, political, and cultural needs. Although indigenous communities have employed sustainable ecosystem management approaches for millennia, ecosystem management emerged formally as a concept in the 1990s from a growing appreciation of the complexity of ecosystems, as well as humans' reliance and influence on natural systems.
Planetary boundaries are a framework to describe limits to the impacts of human activities on the Earth system. Beyond these limits, the environment may not be able to self-regulate anymore. This would mean the Earth system would leave the period of stability of the Holocene, in which human society developed. Crossing a planetary boundary comes at the risk of abrupt environmental change. The framework is based on scientific evidence that human actions, especially those of industrialized societies since the Industrial Revolution, have become the main driver of global environmental change. According to the framework, "transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental-scale to planetary-scale systems."
The United States Environmental Protection Agency (EPA) was established in July 1970 when the White House and the United States Congress came together due to the public's demand for cleaner natural resources. The purpose of the EPA is to repair the damage done to the environment and to set up new criteria to allow Americans to make a clean environment a reality. The ultimate goal of the EPA is to protect human health and the environment.
Ecosystem health is a metaphor used to describe the condition of an ecosystem. Ecosystem condition can vary as a result of fire, flooding, drought, extinctions, invasive species, climate change, mining, fishing, farming or logging, chemical spills, and a host of other reasons. There is no universally accepted benchmark for a healthy ecosystem, rather the apparent health status of an ecosystem can vary depending upon which health metrics are employed in judging it and which societal aspirations are driving the assessment. Advocates of the health metaphor argue for its simplicity as a communication tool. "Policy-makers and the public need simple, understandable concepts like health." Some critics worry that ecosystem health, a "value-laden construct", can be "passed off as science to unsuspecting policy makers and the public." However, this term is often used in portraying the state of ecosystems worldwide and in conservation and management. For example, scientific journals and the UN often use the terms planetary and ecosystem health, such as the recent journal The Lancet Planetary Health.
