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An ongoing current event in which a large number of living species are threatened with extinction or are going extinct because of environmentally destructive human activities. The Earth is presently in the midst of a mass extinction event. In the…

Bats are members of the order Chiroptera, which is the second-largest order of living mammals. The geographic distribution of these flying mammals is tremendous as well, ranging from the limit of trees in the Northern Hemisphere to the southern tips…

Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

Terrestrial and aquatic animals that are capable of excavating holes in the ground for protection from adverse environmental conditions, as well as for storing food. Burrowing animals are uniquely adapted species, having the capacity to dig burrows…

A member of the mammalian family Camelidae in the order Artiodactyla. Camels are even-toed, hoofed mammals (ungulates). There are three extant camel species: the Bactrian camel (Camelus bactrianus; Fig. 1), the wild Bactrian camel (C. ferus), and…

The response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral skeleton visible. Corals (Fig. 1) are animals that live in a partnership (symbiosis) with…

Marine animal life inhabiting the portion of the oceans below the upper limit of the continental slopes. The marine animals that make up the deep-sea fauna live below the photic zone of the oceans. In general, the deep sea may be regarded as that…

Various species of diving, air-breathing animals. Diving animals, which are found in every class of terrestrial vertebrates (amphibians, reptiles, birds, and mammals), are air-breathing species that have almost complete freedom in the aquatic…

The biological study of insects that have a direct influence on humanity. Economic entomology is a subdiscipline of entomology (the biological science that deals with the investigation of insects) and focuses on the effects of insects on human…

The Hudson River estuary in the United States experiences a tide from New York Harbor (river kilometer 0/river mile 0) to Troy, New York (river kilometer 244/river mile 152). In the lower 60 kilometers (37 miles) of the Hudson River, the water is…

A species translocated from one region or continent to another outside its normal range, particularly when the translocation is the result of human activity (intentional or otherwise). Many thousands of species, including animals, plants, fungi,…

The scientific study of parasites and parasitism. Parasitology is the branch of biology dealing with parasitic organisms (see illustration), with particular focus being directed toward understanding the relationship between the parasite and the…

There is a growing body of evidence that many of the thousands of prescription and over-the-counter medications ultimately make their way into water bodies and drinking-water supplies. Typical wastewater treatment plants may not be effective at…

Microplastics are raining down on national parks and other protected areas in the western United States at the rate of about 132 pieces of microplastic per square meter every day, according to a report in the journal Science (June 2020).…

A natural process in which harmful or beneficial effects are caused by secondary metabolites that spread from a donor organism to a recipient and are produced by plants, algae, bacteria, and fungi. Allelopathy is a key ecological process and has…

A discipline within the field of animal behavior that focuses on the reception and use of signals. Animal communication could well include all of animal behavior because a liberal definition of the term signal could encompass all stimuli perceived…

Wildfires, also termed bushfires or forest fires, are currently devastating large swaths of land in Australia. Detrimental ecologic consequences of these uncontrolled combustions of forest fuels and vegetation are numerous. One of the most serious…

The study of behavior change in response to drugs, chemicals, or other environmental conditions or agents. Behavioral toxicology investigates the effect of toxic exposure on organismal behavior. The toxic exposure can involve various chemicals,…

The destruction of organic compounds by microorganisms. Biodegradation is a process (carried out by microorganisms) that decomposes organic material into its constituent elements or new compounds. Microorganisms, particularly bacteria (and fungi to…

A microbial (often bacterial) community that is enveloped by an adhesive substance (the glycocalyx) at the interface of a liquid and a surface. Biofilms (see illustration) are defined as highly structured communities of microorganisms that are…

The study of the cycling of chemicals between organisms and the surface environment of the Earth. The chemicals either can be taken up by organisms and used for growth and synthesis of living matter or can be processed to obtain energy. The chemical…

The use of parasitoids, predators, and pathogens to reduce injurious pest insect populations and consequently the damage that they cause. Biological insect control (or insect biocontrol) is the regulation of insect populations by biological means.…

Management of the human use of natural resources to provide the maximum benefit to current generations while maintaining capacity to meet the needs of future generations. Conservation includes both the protection and rational use of natural…

The world’s oceans and coasts provide a natural sink for excess carbon in the atmosphere. Scientists refer to carbon that is captured and stored this way as blue carbon. Well-known blue-carbon examples include mangroves and salt marshes—wetland…

Pathological conditions affecting the health of coral and causing its physiological dysfunction. Broadly defined, coral disease (Fig. 1) is any impairment to coral health resulting in physiological disturbance and breakdown. It usually involves…

A measure of the three-dimensional structure of live coral communities on reefs. Coral reef structural complexity is an intrinsic element of coral reef ecosystems and quantitates the surface area of coral in relation to its linear area. The…

A large, tawny brown wild cat, Puma concolor (family Felidae), once widespread over most of the Americas; also known as catamount, mountain lion, painter, and puma. The cougar (Puma concolor; see illustration) is a carnivorous member of the family…

Using an artificial intelligence technique known as deep learning and high-resolution remote sensing, scientists have counted and mapped the location of trees in 11,000 satellite images covering more than 1.3 million square kilometers (500,000…

Plants occupying sand dunes and the slacks, or swales, and flats between them. The density and diversity of dune vegetation are greater on coastal dunes than on desert dunes. Dune Plant geography Sand Zonation A zonation pattern is evident in the…

The biological sonar that bats, toothed whales, and certain other animals use to navigate without the visual system. Echolocation, or biosonar, is the physiological process that certain animals use to locate objects by reflected sound, primarily in…

The interaction of at least two organisms or species such that, for each, the birth or growth rates are depressed and the death rate increased by the presence of the other organisms or species. Ecological competition is the conflict that arises…

The study of the flow of energy within an ecological system from the time the energy enters the living system until it is ultimately degraded to heat and irretrievably lost from the system. It is also referred to as production ecology, because…

The methods required for the measurement of features of plant and animal populations or for quantifying energy flow or other aspects of ecological communities. Ecologists are concerned with such a wide range of variables that they may use many other…

The use of computer simulations or mathematical equations to address questions that cannot be answered solely by experiments or observations. Ecological models have two major aims: to provide general insight into how ecological systems or ecological…

A directional change in an ecological community. Populations of animals and plants are in a dynamic state. Through the continual turnover of individuals, a population may expand or decline depending on the success of its members in survival and…

An obligate association formed between the roots of many plant species, especially trees, and a diverse range of soil fungi. The fungi and the finest, terminal root tips interact to form joint organs called ectomycorrhizas (Fig. 1). In…

A peculiar order of silk-spinning, orthopteroid insects, commonly called the embiids or web spinners, which are related to termites. The order Embioptera (also known as Embiidina or Embiodea) comprises about 300–400 described species, which are…

The sum of all external factors, both biotic (living) and abiotic (nonliving), to which an organism is exposed. All of the outside factors to which an organism is exposed comprise its environment (Fig. 1). The environment has a tremendous influence…

The name given to any of three carnivorous mammals in the genus Mustela (family Mustelidae); also known as the polecat. There are three species of ferrets, also termed polecats, belonging to the genus Mustela in the family Mustelidae of the order…

A group of grasses belonging to the genus Festuca used for both hay and pasture. There are approximately 100 species of fescue, and more than 30 are represented in the United States. Tall fescue (F. arundinacea; alternatively Lolium arundinaceum),…

The trees, shrubs, herbs, bacteria, fungi, and animals, together with the surrounding air, soil, water, organic debris, and rocks (environmental substrate), interacting inside a defined boundary. Forests and woodlands occupy about 38% of the Earth's…

A physiologically interactive system within which growth, adaptation, species composition, nutrient cycling, biological productivity, and energy flows among inland aquatic microbial, plant, and animal communities are integrated with the environment.…

A large and diverse order of conspicuous brown algae (class Phaeophyceae), including such well-known seaweeds as Fucus and Sargassum. Definitive features of members of the Fucales include apical growth, production of sex organs in cavities, and a…

The subdiscipline in mycology and ecology that examines community composition and structure; responses, activities, and interactions of single species; and the functions of fungi in ecosystems. The fungi, as they have been historically classified,…

A group within the cnidarian subclass Octocorallia (class Anthozoa), comprising organisms known as gorgonians. Common names for members of the Gorgonacea (Figs. 1–5) include sea rods (Fig. 4a), sea fans (Fig. 4b), sea feathers (Fig. 4c), bamboo…

A biological community that contains few trees or shrubs, is characterized by mixed herbaceous (nonwoody) vegetation cover, and is dominated by grasses or grasslike plants. Grasslands are areas of herbaceous terrestrial vegetation dominated by…

A desert plant, Parthenium argentatum, cultivated as a source of rubber. Guayule belongs to the aster family (Asteraceae). It is a native perennial shrub that grows in the Chihuahuan Desert of north-central Mexico and southwestern Texas. The plant…

A group of species that utilize the same kinds of resources, such as food, nesting sites, or places to live, in a similar manner. Emphasis is on ecologically associated groups that are most likely to compete because of similarity in ecological…

The requirement of high salt (NaCl) concentrations for growth of microorganisms. Microorganisms (mainly bacteria) can be classified by their physiological tolerance to salt (Fig. 1). Most normal bacteria, such as Escherichia coli, and most…

The consumption of living plant tissue by animals. Plants and the animals that consume them constitute roughly one-half of the scientifically described species. Herbivorous species occur in most of the major taxonomic groups of animals, including…

The largest subclass in the class Bivalvia, phylum Mollusca. The subclass Heterodonta contains some of the most ecologically important bivalves (Fig. 1). For example, marine clams, cockles, and shipworms are heterodonts. Formerly, the class Bivalvia…

The branch of ecology that considers the relations of individual persons and human communities with their particular environment. Human ecology is concerned with learning how the distributions and numbers of humans are determined by interactions…

Conservationists are alarmed by significant reductions in insect populations worldwide. Based on recent biodiversity surveys and entomological studies, scientists estimate that more than 40% of the world's insect species (class Insecta, phylum…

The study of the establishment, spread, and ecological impact of species translocated from one region or continent to another outside their normal range, particularly when the translocation is the result of human activity (intentional or otherwise).…

Alien species whose introduction does or is likely to cause environmental or economic harm to forests. Nonnative organisms that cause a major change to native ecosystems are generally referred to as invasive species or invasives; they also are…

The distribution of plants and animals on islands. Islands harbor the greatest number of endemic species. The relative isolation of many islands has allowed populations to evolve in the absence of competitors and predators, leading to the evolution…

A predatory, cosmopolitan cetacean mammal, Orcinus orca, found typically in cold ocean waters. Killer whales (Orcinus orca) [Fig. 1] are top (apex) predators in the marine ecosystem, with no natural enemies other than humans. These carnivorous…

An order of large brown algae (class Phaeophyceae) commonly called kelps. Definitive features of members of the Laminariales include a life history in which microscopic, filamentous, dioecious gametophytes alternate with a massive, parenchymatous…

The process by which seriously disturbed land surfaces are stabilized against the hazards of water and wind erosion. All seriously disturbed land areas are in need of reclamation and should be stabilized and reclaimed as quickly as possible after…

Categories of land resources that provide information about uses and characteristics. In combination with geographic location systems, measurements of the amount of land in use, the amount available for development, and the changes in use over time,…

The long-term development or conservation of an area and the establishment of a relationship between local objectives and regional goals. Land-use planning (see illustration) is often guided by laws and regulations. The legal basis of land-use…

Symbiotic associations of fungi (mycobionts) and photosynthetic partners (photobionts). Lichens (Fig. 1) consist of fungi and algae or cyanobacteria growing together symbiotically. Lichen associations always result in a distinct morphological body…

A term for the vegetative (morphological) form of the plant body. A related term is growth form but a theoretical distinction is often made: life form is thought by some to represent a basic genetic adaptation to environment, whereas growth form…

Any of the taxonomically diverse trees and shrubs that form the dominant plant communities in tidal, saline wetlands along sheltered tropical and subtropical coasts. The various species of mangrove trees and shrubs are important ecological community…

The management of marine species and ecosystems to prevent their decline and extinction. As in terrestrial conservation, the goal of marine conservation is to protect biodiversity and ecosystem function through the preservation of species,…

An integrative science that studies the basic structural and functional relationships within and among living populations and their physical–chemical environments in marine ecosystems. Although an outgrowth of natural history and the life sciences,…

The harvest of animals and plants from the ocean to provide food for people and animals. Marine fisheries are places or industries engaged in the harvesting of aquatic life in seawaters. Important products in marine capture fisheries include fish…