What Is Ecology?

Ecology is the scientific study of the interactions among living organisms and between organisms and their physical environment. It operates across multiple levels of biological organization, from individual organisms and their physiological responses to environmental conditions, through populations and communities, to entire ecosystems and the biosphere. Ecology seeks to explain patterns of abundance, distribution, and diversity of life, and to identify the processes, including competition, predation, nutrient cycling, and disturbance, that generate those patterns. As a discipline, it draws from evolutionary biology, physiology, mathematics, hydrology, and atmospheric science.

The NSF Division of Environmental Biology supports foundational ecology research across scales ranging from population dynamics and species interactions to large-scale ecosystem processes, reflecting the discipline's breadth and its importance to both basic science and applied environmental management.

Population and Community Ecology

Population ecology examines how groups of individuals of a single species change in size and composition over time, using demographic models to relate birth rates, death rates, immigration, and emigration to environmental drivers such as resource availability and predator abundance. Community ecology considers the set of species coexisting in a given location and studies the interactions, including predation, parasitism, mutualism, and competition, that determine which species persist and at what densities. Biodiversity, measured both as species richness and as the relative abundance distribution across species, is a central quantity in community ecology because it is linked to ecosystem stability, productivity, and resilience to disturbance. The NSF Population and Community Ecology Cluster funds research investigating how these species-level dynamics operate across space and time, including in the context of habitat fragmentation and climate-driven range shifts.

Ecosystem Ecology and Entomology

Ecosystem ecology examines fluxes of energy and materials through biological and physical systems, using measures such as net primary productivity, nutrient cycling rates, and carbon storage rather than species identities as primary currency. The trophic structure of an ecosystem, organized into producers, consumers, and decomposers, determines how energy captured from sunlight moves through the food web and how much is available at each level. Entomology, the study of insects, is deeply embedded in ecosystem ecology because insects occupy critical functional roles across trophic levels. Insects are pollinators for over 85% of wild flowering plant species, decomposers that process plant litter and organic matter, prey for vertebrate insectivores, and biological control agents for other herbivorous insects. The Entomological Society of America's position statement on insects and biodiversity emphasizes that healthy ecosystem functions, including clean water, productive soils, and crop pollination, depend on diverse and abundant insect communities.

Environmental Monitoring and Applied Ecology

Applied ecology uses the principles of population, community, and ecosystem ecology to address environmental problems including habitat loss, invasive species management, pollution remediation, and sustainable land use. Biomonitoring programs use indicator species, particularly macroinvertebrates, fish, and birds, to assess ecosystem health because species composition responds predictably to environmental stressors such as nutrient loading, sedimentation, and chemical contamination. Remote sensing and geographic information systems have extended ecological measurement to continental and global scales, enabling satellite-based tracking of land cover change, vegetation phenology, and primary productivity. Long-term ecological research networks, such as the LTER sites supported by NSF, generate decadal datasets that reveal slow-moving processes invisible in short-term studies.

Applications

Ecology has applications across natural resource management, engineering, and policy domains, including:

• Conservation planning for protected area design and species recovery programs
• Agricultural pest management using integrated pest management and biological control
• Ecological risk assessment for industrial site remediation and environmental permitting
• Urban green infrastructure design for stormwater management and urban heat island reduction
• Climate impact modeling for forest carbon accounting and land-use change scenarios