adaptation Process of genetic change within a population due to natural selection, whereby the average state of a character becomes better suited to some feature of the environment.

adaptive management The practice of revisiting management decisions and revising them in the light of new information.

adequacy A single reserve that is large enough to fulfill its conservation functions, or in a reserve system, a sufficient number or area of reserved sites to achieve conservation objectives.

agroecosystem Land used for crops, pasture, and livestock; the adjacent uncultivated land that supports other vegetation and wildlife; and the associated atmosphere, the underlying soils, groundwater, and drainage networks.

Allee effect The phenomenon where at the point when population density is too low for individuals to find mates, reproductive success sharply declines.

allele One of a pair of genes at a particular genetic locus. Different alleles are usually named for having a specific phenotypic affect (e.g., wild type versus mutant, albino versus normal, fine-spot versus large-spot).

allopatric Describes two or more populations or species that occur in geographically separate areas. See also sympatric.

allozyme One of several possible forms of an enzyme that is the product of a particular allele at a given gene locus.

alpha- or α-richness The number of species occurring within a given habitat.

alternative-futures analysis A form of conservation planning where stakeholders and conservation biologists work together to propose and examine the consequences of distinct possible future states for an area, and use these projections as a basis for land use planning.

anthropocentrism Any human-oriented perspective of the environment, but usually used to emphasize a distinction between humans and nonhumans. For example, assessing a tropical forest in terms of its potential timber value is an exclusively anthropocentric perspective.

anthropogenic climate change The change in global, regional, and local climate as a result of human activities. Often referred to only as climate change or global warming.

area/perimeter ratio The ratio of internal area to edge habitat of a region. The area/perimeter ratio is an indication of the amount of interior habitat with respect to edge habitat, and may indicate potential success of a reserve in protecting interior species.

augmentation Restoration undertaken to expand a site in area or quality.


background extinction rate
Historical rates of extinction due to environmental causes not influenced by human activities, such as the rate of species going extinct because of long-term climate change.

Bayesian statistics A branch of modern statistics that bases statistical inferences and decisions on a combination of information derived from observation or experiment and from prior knowledge or expert judgment. Contrast this approach with classical statistics, which regards only the data from observations or experiments as useful for estimation and inference.

beta or β-richness The change or turnover of species from one habitat to another.

bequest value This is the value that people place on goods that they may wish to save for future generations, usually similar to existence value.

biocentrism A perception of the world that values the existence and diversity of all biological species, as opposed to a human-centered perspective (anthropocentrism).

biodiversity The variety of living organisms considered at all levels of organization, including the genetic, species, and higher taxonomic levels; and the variety of habitats and ecosystems, as well as the processes occuring therein.

biological control The use of a species to consume or otherwise control the population of a pest or invasive species.

biological integrity The ability to support and maintain balanced, integrated, functionality in the natural habitat of a given region.

biome A large, regional ecological unit, usually defined by some dominant vegetative pattern, such as the coniferous forest biome.

Biosphere Reserve A concept of reserve design in which a large tract of natural area is set aside, containing an inviolate core area for ecosystem protection, a surrounding buffer zone in which nondestructive human activities are permitted, and a transition zone in which human activities of greater impact are permitted. Three goals of a biosphere reserve are conservation, training (education), and sustainable human development compatible with conservation.

buffer zone An area in a reserve surrounding the central core zone, in which nondestructive human activities such as ecotourism, traditional (low-intensity) agriculture, or extraction of renewable natural products, are permitted.

bushmeat Meat from animals, including edible invertebrates, that is harvested in the wild.


cascade effect
The phenomenon where the extinction or change in abundance of a species causes changes in the abundance or extinction of many other species, which in turn causes such changes in still more species.

cladistics A system of classification based on historical (chronological) sequences of divergence from a common ancestor.

cladogram A diagram of cladistic relationships. An estimate or hypothesis of true genealogical relationships among species or other groupings.

coadapted gene complex A concept in which particular genes from multiple loci have coevolved to collectively enhance fitness under a given set of environmental conditions.

commons Originally referred to lands in medieval Europe that were owned by townships rather than by private individuals. Now used to include any exploitable resource that is not privately owned. Sometimes applied to so-called “open resources” that are neither privately owned nor regulated by a country or agency.

community-based conservation (CBC) A conservation approach that is rooted in local community development, is highly participatory, and seeks to make both conservation and development goals primary.

comprehensiveness In a reserve system context, a site selection process that includes many or most biodiversity features (e.g., species, ecological communities).

conservation biology An integrative approach to the protection and management of biodiversity that uses appropriate principles and experiences from basic biological fields such as genetics and ecology; from natural resource management fields such as fisheries and wildlife; from social sciences such as anthropology, sociology, philosophy, and economics; as well as other fields such as the creative arts and communications.

constructed market approach Also known as hypothetical market approach. Used in contingent valuation to express nonmarket values. For example, by determining a representative population’s willingness to pay to save a natural area or species a hypothetical market value can be assigned.

contingent valuation method (CVM) Uses questionnaires and other inquiry methods to find nonmarket or indirect market values. Often expressed as a question, “How much would you be willing to pay to save the Artic National Wildlife Refuge?” See also willingness to pay.

conventional market approach Assigns a market value to environmental goods or services by comparing them to similar goods and services that have known market values. The general methods include opportunity costs, production-function, and substitute/alternative cost.

cost–benefit analysis (CBA) A method of evaluating projects by assessing all project costs and benefits, usually in monetary units, over the lifetime of the project. See also discounting and net present value.

critical habitat According to U.S. Federal law, the ecosystems upon which endangered and threatened species depend.

critical natural capital A precautionary approach that argues that certain environmental goods, services, and species are too important to be traded for gains in other forms of capital (e.g., financial, human-generated goods, human capital). Critical natural capital is said to be non-substitutable. An example might be the last remaining population of an endangered species.


The aggregate desire for economic goods and services. The quantity of a good or service that consumers are willing to purchase at different prices. Demand involves the relationship between quantity and price.

deme A randomly interbreeding (panmictic) local population.

demographic bottleneck A significant, usually temporary, reduction in genetically effective population size, either from a population “crash” or a colonization event by a few founders.

demographic PVAs See population viability analysis.

demographic uncertainty Chance populational events, such as sex ratios or the act of finding a mate that influence survival in small populations.

density-dependent factors Life history or population parameters that are a function of population density.

density-independent factors Life history or population parameters that are independent of population density.

development Formation of human, social, financial or man-made capital; need not be equivalent to economic growth. See also steady state economics.

direct use value The value we receive by using some part of the environment. For example, logging is a direct use value of a forest.

discounting The technique of placing a value on a project or resource at different times in the future. A high discount rate assumes that current values will decline rapidly in the future.

dominance The condition when an allele exerts its full phenotypic effect despite the presence of a different allele at the same locus. For example, if allele A is dominant over a, then genotypes AA and Aa will have the same phenotype.


ecocentric value
The value of ecological entities irrespective of their usefulness to humans.

ecological-economic efficiency This is the ratio of man made capital services gained to natural capital services lost as a result. Clear-cutting a watershed results in poor efficiency. Sustainable logging would have higher efficiency.

ecological footprint The impact a human community or nation has in terms of the amount of land or sea needed to produce the resources consumed.

ecological indicator A characteristic of an ecosystem that is related to, or derived from, a measure of biotic or abiotic variable that can provide quantitative information on ecological structure and function. An indicator can contribute to a measure of integrity and sustainability.

ecological integrity A living system exhibits integrity if, when subjected to disturbance, it sustains and organizes self-correcting ability to recover the state that is normal for that system. See also biological integrity.

ecological release Habitat expansion or density increase of a species when one or more competing species are not present.

ecological restoration The process of using ecological principles and experience to return a degraded ecological system to a more ecologically functional state. The goal of this process is to emulate the structure, function, diversity, and dynamics of the specified ecosystem.

ecologically functional population A population that is of sufficient size to fulfill its ecological roles.

ecoregion A relatively large area of land or water that contains a geographically distinct assemblage of natural communities.

ecosystem management An approach to maintaining or restoring the composition, structure, and function of natural and modified ecosystems for the goal of long-term sustainability. It is based on a collaboratively developed vision of desired future conditions that integrates ecological, socioeconomic, and institutional perspectives, applied within a geographic framework defined primarily by natural ecological boundaries.

ecosystem service The conditions and processes of natural ecosystems and species that provide some, usually utilitarian, human value. As examples, riparian swamps protect downstream property from flood damage or wild bees pollinate certain food crops. Ecosystem services are examples of indirect use values.

ecotourism Nature-based tourism; sometimes visiting new cultures is included in the definition.

edge effect The negative influence of a habitat edge on interior conditions of a habitat, or on species that use interior habitat. Also, the effect of adjoining habitat types on populations in the edge ecotone, often resulting in more species in the edge than in either habitat alone.

efficiency Achieving conservation objectives with the least possible cost. In a reserve system this often equates to minimizing the number of sites that need protection.

efficient allocation An economic term that refers to the market’s ability to match resources with material ends. The apportionment of resources to the production of different goods and services.

endangered species Species threatened with extinction by anthropogenic or natural changes in their environment. Requirements for declaring a species globally Endangered are described in the IUCN Red List. Countries often also have legal requirements for designating a species as endangered, such as in the U.S. Endangered Species Act. According to U.S. Federal law, an endangered species is a species in imminent danger of extinction throughout all or a significant portion of its range.

endemic Any localized process or pattern, but usually applied to a highly localized or restrictive geographic distribution of a species.

enhancement Management technique (seeding, transplantation, fencing, watershed manipulations, etc.) that attempts to restore to predisturbance conditions those areas only partially disturbed by human influence.

environmental impact assessment (EIA) An analysis of the total beneficial and negative impacts of a project on the environment.

environmental modification Modification of the phenotype as a result of environmental influences on the genotype.

environmental uncertainty Unpredictable sources of density-independent mortality, such as an early snowstorm, that jeopardize the survival of a small population by pushing it below its minimum viable population size.

epistasis Interactions among alleles at two or more loci that affect the state of a single trait, where the combined effects differ from the sum of the individual locus effects.

equilibrium A state reached when a population’s birth and immigration rates are equal to its mortality and emigration rates. Also applied to species changes in a community or to any other ecological process in which the rate of increase equals the rate of decrease, resulting in a steady state.

eutrophication Naturally, the slow aging process during which a lake, estuary, or bay evolves into a bog or marsh and eventually disappears. During the later stages of eutrophication the water body is choked by abundant plant life due to higher levels of nutritive compounds such as nitrogen and phosphorus. Human activities can accelerate the process, leading to rapid algal growth, and later hypoxia.

evolutionarily significant unit (ESU) Partially genetically differentiated populations that represent a significant component of the evolutionary legacy of the species and that are considered to require management as separate units.

Evolutionary-Ecological Land Ethic A philosophical approach to conservation derived from the evolutionary and ecological perspective, first advanced by Aldo Leopold. Nature is seen not as a collection of independent parts, to be used as needed, but as an integrated system of interdependent processes and components, in which the disruption of some components may greatly affect others. This ethic is the philosophical foundation for modern conservation biology.

existence value The value, usually nonmarket, that is assigned by society to a place or species simply because its existence is considered important. For example, the Arctic Wildlife Refuge has a significant existence value for many people even though they may never visit it.

exploitation The consumptive use of any natural resource.

ex situ conservation Conservation efforts that take place in zoos, aquaria, greenhouses, or in other facilities. Usually involves storing and rearing individuals or genetic material for future reintroduction. Contrast with in situ conservation.

externality A cost, usually in terms of environmental degradation, that results from an economic transaction but which is not included as a debit against economic returns.

extinction threshold A population size or density below which a population becomes at risk of immediate extinction. Used to describe the phenomenon when risk of extinction rises sharply with only a small change in population size or number of habitat patches occupied.


Refers to a system whose output modifies input to the system. Prices play this role in market systems.

fitness The relative contribution of an individual’s genotype to the next generation in the context of the population’s gene pool. Relative reproductive success.

fixation All individuals in a population are identically homozygous for a locus (e.g., all A1A1).

founder effect The principle that the founders of a new population carry only a random fraction of the genetic diversity found in the larger, parent population. Change in the genetic composition of a population due to founding or origin from a small number of individuals.

fragmentation See habitat fragmentation.

Fundamental Theorem of Natural Selection The basic theorem of population genetics, which states that the rate of evolutionary change in a population is proportional to the amount of genetic diversity (specifically, additive genetic variance) available in the population.


gamma- or γ-richness
The number of species found within a large region, which typically includes several habitats.

GAP analysis The use of various remote sensing data sets to build overlaid sets of maps of various parameters (e.g., vegetation, soils, protected areas, species distributions) to identify spatial gaps in species protection and management programs.

gene flow The uni- or bidirectional exchange of genes between populations due to migration of individuals and subsequent successful reproduction in the new population.

gene locus The site on a chromosome occupied by a specific gene. See also locus.

gene pool Group of interbreeding adults and progeny that collectively represent the bank of genetic material available in the population for future adaptation.

genetic drift Random changes in population allele frequency and levels of genetic diversity due to the finite number of individuals contributing genes to the next generation.

genetically effective population size (Ne) The number of individuals that would result in the same level of inbreeding, or decrease in genetic diversity through drift, if the population behaved in the manner of an idealized and randomly mating population. The functional size of a population, in a genetic sense, based on numbers of actual breeding individuals and the distribution of offspring among families. Ne is typically smaller than the census size of the population.

genotype The entire genetic constitution of an organism, or the genetic composition at a specific gene locus or set of loci.

geographic information system (GIS) A computerized system of organizing and analyzing any spatial array of data and information.

geographic variation Change in a species’ trait over distance or among different distinct populations. Measurable character divergence among geographically distinct populations that are often, though not necessarily, the result of local selection.

geostatistics A form of spatial statistics originally created for analyzing irregular geological features. Now used in ecology to create probability maps from a limited set of location-specific data points.

grain Refers to how organisms perceive spatial heterogeneity. The more time that an organism spends in any particular kind of environment, the more coarsely grained that environment is said to be.

greenhouse gas A gas, such as carbon dioxide or methane, which contributes to potential climate change.

growth In conventional economics, any rate of increase in value that exceeds the rate of inflation.


habitat degradation
The decrease in the quality of an area due to human activities.

habitat fragmentation The disruption of extensive habitats into isolated and small patches; or the result of development in a large area where habitat is now fragmented into separate units; often applied to forested habitats that have been fragmented by agricultural development or logging.

habitat loss The conversion or transformation of a natural area into a wholly human occupied area of little or no use to wild species.

habitat shredding A form of habitat fragmentation in which the fragments often remain as strips or “shreds” in ravines and other inaccessible areas.

Hardy-Weinberg equilibrium The stability of gene frequencies expected in a sexual, diploid population when a number of assumptions are met, including random mating, a large population, and no migration, mutation or selection.

harvesting Collecting any natural resource, usually biological, for exploitation.

hedonic pricing (HP) Recognizes that goods may be described by an array of objectively measurable characteristics. For example, the price of a house may be made up of the prices ascribed to the number and size of rooms, the size of the garden, the quality of local services and the nature of the surrounding environment. See implicit market approach.

heritability The proportion of observed variation in phenotype that can be attributed to differences in genotype.

heterosis Hybrid vigor or superior performance of hybrid genotypes, usually based on comparison to parental genotypes. Heterosis often results from the masking of deleterious alleles that occur in a homozygous state in high frequency in populations. Sometimes called hybrid vigor.

heterozygosity A measure of the genetic diversity in a population, as measured by the number of heterozygous loci across individuals.

heterozygous The condition in which an individual has two different alleles at a given gene locus (e.g., Aa). Heterozygous individuals can produce two different gametes.

heuristic algorithm A set of ordered steps for solving a problem whose general purpose is not to find a optimal solution, but an approximate solution where the time or resources to find a perfect solution are not practical.

hierarchical analysis of genetic diversity An approach to defining population genetic structure for a species in nature that defines components of total genetic diversity in a spatially hierarchical fashion. Genetic diversity can be apportioned in a hierarchical fashion (e.g., alleles within individuals, individuals within populations, populations within regions) to accomplish this goal.

homoplasy Possession by two or more species (or groups) of a similar or identical trait that has not been derived by both species (or groups) from their common ancestor. Homoplasy could result from convergence, parallel evolution, or character reversal.

homozygous Individual having two copies of the same allele at a locus (AA or aa). The individual is genetically invariant because it can produce only one kind of gamete.

hotspot A geographic location characterized by unusually high species richness, often of endemic species.

hybrid vigor See also heterosis.

hypoxia/hypoxic waters Waters with dissolved oxygen concentrations of less than 2 ppm, the level generally accepted as the minimum required for most marine life to survive and reproduce.


An equation describing the total impact of humans on natural systems as a function of population size (P), level of affluence (A), and technological sophistication employed (T).

implicit market approach Assigns market values to goods and activities that include the perceived value of the environment. For example, one might accept less wages to wait tables in a national park restaurant because the surrounding environment has perceived value. Two common methods are travel cost and hedonic pricing.

inbreeding The mating of individuals who are more closely related than by chance alone, such as relatives. Also the correlation of genes within individuals relative to that expected if individuals had mated at random.

inbreeding depression A reduction in fitness and vigor of individuals as a result of increased homozygosity through inbreeding in a normally outbreeding population.

indicator species or taxon A species or higher taxonomic group used as a gauge for the condition of a particular habitat, community, or ecosystem. A characteristic, or surrogate species for a community or ecosystem.

indirect use value The value, either market or nonmarket, that is provided by an environmental service. See also option value.

inherent value See intrinsic value.

in situ conservation Conservation efforts that take place in the wild. Contrast with ex situ conservation.

instrumental value The worth of an entity as judged by its utility or usefulness to humans.

integrated conservation and development project (ICDP) A term applied to large conservation projects that have the dual goal of improving people’s livelihoods while protecting biodiversity and ecosystem functions.

intermediate disturbance hypothesis An hypothesis (with good empirical support) that posits that maximum species richness in many systems occurs at an intermediate level (of intensity or frequency, or both) of natural disturbance.

intrinsic value The worth of an entity independent from external circumstances or its value to humans; value judged on inherent qualities of an entity rather than value to other entities.

invasive species A nonnative species that spreads rapidly and outcompetes, preys on and otherwise reduces or eliminates populations of native species.

irreplaceability A conservation element that is nonsubstitutable, that is, an element that must be protected if conservation goals are to be met.


keystone mutualist species
Keystone species that perform a mutualistic function, such as plant species that are broadly used as pollen sources.

keystone species A species whose impacts on its community or ecosystem are large, and much larger than would be expected from its abundance.


land-bridge island
Areas that are presently island habitats, but were formerly connected to the mainland during periods of lower ocean levels. Land-bridge islands tend to lose species over time in a process called “relaxation.”

landscape matrix The intervening area among a set of habitat fragments. Also the spatial array of habitats across a landscape.

landscape species approach A conservation approach developed by the Wildlife Conservation Society that uses wide-ranging focal species to design conservation efforts over a large landscape with both conservation and human uses.

linear programming (LP) A mathematical approach that finds the optimal solution (e.g., maximum net profit) by changing the values of the various constraints. For example, the optimal critical habitat for a species might be determined by varying the constraints of reserve size, migration corridors, food abundance, and density of predators to determine which combination of real constraints provides the critical habitat with the highest probability of survival for the species in question.

locus Physical location occupied by a gene on a chromosome. Used interchangeably with gene. See gene locus.


marine protected areas (MPAs)
A marine site in which some or all human uses are prohibited.

mass extinction The extinction of large numbers of taxa during a relatively brief geologic time frame, such as the extinction of dinosaurs at the end of the Cretaceous Period.

mate choice Form of sexual selection where one sex (usually females) determines whether mating occurs or not, often on the basis of phenotypic or behavioral characteristics of the opposite sex.

maximum sustained yield (MSY) The largest harvest level of a renewable resource that can be sustained over a period of many generations. Harvest of a natural population at the population size representing the maximum rate of recruitment into the population, based on a logistic growth curve.

mesopredators Refers to medium-sized predators, such as raccoons and foxes, that often increase in abundance when larger predators are eliminated.

metapopulation A network of semi-isolated populations with some level of regular or intermittent migration and gene flow among them, in which individual populations may go extinct but can then be recolonized from other populations.

minimum dynamic area The smallest area necessary for a reserve to have a complete, natural disturbance regime in which discrete habitat patches may be colonized from other patches within the reserve.

minimum viable population (MVP) The smallest isolated population that has a specified statistical chance of remaining extant for a specified period of time in the face of foreseeable demographic, genetic, and environmental stochasticities, plus natural catastrophes.

monetizing The process of placing monetary value on typically non-monetary goods and processes such as biological material or ecological processes. The process of converting values to economic units.

monomorphic Presence of only one allele at a locus. Lack of genetic diversity. Contrast wth polymorphic.

morphospecies Species that are distinguished on the basis of appearance; often used in field studies when taxonomies and keys are incomplete; a morphospecies is not a formal taxonomic entity.

multi-criteria analysis Similar to linear programming but more than one criterion is optimized. For example, one might want to jointly optimize the combination of tourist access and habitat quality for a species that has value for ecotourism.

multiple gene traits Those traits whose phenotype is affected by many genes. Also called polygenic traits. Often form continuous distributions (e.g., length, weight, condition factor).

multiple use concept Refers to the simultaneous and compatible use of public land and water resources by different interest groups. For example, U.S. public law requires that national forests be open to recreational use, timber extraction, mining or other concessions, and biodiversity protection. In reality, the activities of the various interest groups generally conflict, and are often incompatible with biodiversity protection.

mutation A spontaneous change in the genotype of an organism at the genetic, chromosomal, or genomic level, usually caused by errors in replication. “Mutation” usually refers to alterations to new allelic forms, and represents new material for evolutionary change, although most mutations are either mildly or strongly deleterious.

mutational meltdown The decline in reproductive rate and downward spiral towards extinction due to chance fixation of new mildly deleterious mutations in small populations.

mutualism An interspecific relationship in which both organisms benefit; frequently a relationship of complete dependence. Examples include flower pollination and parasite cleaning.


natural catastrophe
A major environmental cause of mortality, such as a volcanic eruption, that can affect the probability of survival for both large and small populations.

natural selection A process by which differential reproductive success of individuals in a population results from differences in one or more hereditary characteristics. Natural selection is a function of genetically based variation in a trait, fitness differences (differential reproductive success) among individuals possessing different forms of that trait, and inheritance of that trait by offspring.

nested subset A pattern of species biogeographic distribution in which larger habitats contain the same subset of species in smaller habitats, plus new species found only in the larger habitat. Common species are found in all habitat sizes, but some species are found only in progressively larger habitats.

net present value (NPV) This is the cumulative value of a project when all costs and benefits are discounted over the lifetime of the project. By comparing alternative projects, the one with the highest NPV has the highest net benefits.

net primary productivity (NPP) Net production of plant biomass, and the basis of all food webs.

neutral genetic variation Genetic variation (alleles or genotypes) that is not or appears not to be subject to natural selection.

nonequilibrium A condition in which the rate of increase does not equal the rate of decrease. In nonequilibrial population growth, environmental stochasticity disrupts the equilibrium.

nonuse value See existence value.

nutrient pollution Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.


opportunity cost
The value forgone when not taking a particular option. When choosing one option precludes other options, the value assigned to those other options is the opportunity cost.

opportunity cost approach Uses conventional markets to assign forgone value when one action is taken over another. For example, protecting trees in a reserve may have many benefits but it also has an opportunity cost in the form of forgone timber sales.

option value An economic term that refers to assigning a value to some resource whose consumption is deferred to the future; the value placed on environmental assets by people who want the use of it in the future. Yet to be discovered medicinal plants means that rainforests have an option value.

outbreeding depression Reduction in reproductive fitness due to crossing of individuals from two genetically differentiated populations.

overexploitation The consumptive use of a natural resource beyond its capacity to replenish what has been taken.

overdominance The condition in which a heterozygote at a given locus has higher fitness than either homozygote. Also called heterozygote superiority.


Exhibiting random breeding among individuals of a population.

paradigm An established pattern of thinking. Often applied to a dominant ecological or evolutionary viewpoint; e.g., during earlier decades, the dominant paradigm in ecology held that communities were shaped by equilibrial processes.

patch dynamics A conceptual approach to ecosystem and habitat analysis that emphasizes dynamics of heterogeneity within a system. Diverse patches of habitat created by natural disturbance regimes are seen as critical to maintenance of diversity.

pedigree Multigenerational chart of parent–offspring relationships.

pedigree analysis Use of pedigrees in conservation planning, particularly for captive propagation, to avoid inbreeding and maximize genetic diversity.

phenotype The physical expression (outward appearance) of a trait of an organism, which may be due to genetics, environment, or an interaction of the two.

philopatry Individuals returning to the same area to breed.

phylogenetic diversity (PD) The evolutionary relatedness of the species present in an area.

phylogeny The evolutionary or cladistic relationships among species or higher taxa; the relatedness through descent of any taxon; e.g., the phylogeny of birds leads back to certain lines of dinosaurs.

phylogeographic Evolutionary relationships among species populations based on geographic relationships and historical gene flow patterns.

phylogeography Study of the geographical distribution of genealogical lineages, especially within species.

plasticity The condition of genetically based, environmentally induced variation in characteristics of an organism.

pleiotropy One gene affects two or more traits.

pluralism A school of thought which holds that species concepts should vary with the taxon under consideration. Many different species definitions would be employed.

point richness The number of species found at a single point in space.

policy briefs Policy briefs are concise analyses designed to give legislators and other decision-makers key features of a particular policy. Sometimes briefs are given to the news media.

policy statements Provides an administration’s or an NGO’s position on a particular policy.

polymerase chain reaction (PCR) A process in which a particular DNA segment from a mixture of DNA chains is rapidly replicated, producing a large, readily analyzed sample of a piece of DNA; the process is sometimes called DNA amplification.

polymorphic More than one allele at a genetic locus. Contrast with monomorphic.

polyploidy Possessing more than two complete sets of chromosomes.

population viability analysis (PVA) A quantitative analysis of the many environmental and demographic factors that affect survival of a population, usually applied to small populations at risk of extinction.

position paper An in-depth analysis to support policy briefs and policy statements.

precautionary principle The principle that when information about potential risks is incomplete, decisions about the future policies should be based on a preference for avoiding unnecessary environmental or health risks.

prescribed burn The process of burning an area of land to suppress or kill certain plant species and to favor the growth of others, resulting in a desired plant community.

present value (PV) The value of a project at any point in the future determined by subtracting costs from benefits and multiplying by the discount rate. See also net present value.

production function approach Uses conventional markets to assign a value to some change in environmental conditions that affect productivity. For example, the value of reforesting a watershed could be expressed in the market value from increases in crop production that results from a more abundant water supply.

protected area A site where human uses are restricted or prohibited and where conservation of biodiversity is a primary goal.


quantitative genetics
The study of phenotypic traits that are influenced by multiple genetic and environmental factors (polygenic traits).


A revegetation or land management goal that includes a lower diversity of species and may include substitutions by introduced species.

re-creation The act of entirely reconstructing a site denuded of its terrestrial and/or aquatic systems. This commonly occurs on surface mined lands and in brownfields (severely damaged urban and industrial lands). Also termed creation, but creation implies transforming a site to a completely different ecosystem than had previously existed on the site.

rehabilitation Creation of an alternative ecosystem following a disturbance, different from the original and having utilitarian rather than conservation values. To repair damaged or blocked ecosystem functions, with the primary goal of raising ecosystem productivity for the benefit of local people.

reintroduction An attempt to establish a species in an area which was once part of its historical range, but from which it has been extirpated or become extinct.

regional scale The largest scale of corridors in which major swaths of habitat connect regional networks of reserves.

relaxation The loss of species on land-bridge islands following separation from the mainland or the loss of species during any process of habitat fragmentation and isolation.

remediation Removal of toxicants from a contaminated environment using chemical, physical, or biological means.

remote sensing Any technique for analyzing landscape patterns and trends using low altitude aerial photography or satellite imagery. Any environmental measurement that is done at a distance.

representativeness In a reserve system, the quality of a set of sites that together include all or most biodiversity elements (e.g., species or ecological communities).

rescue effect The recolonization of a habitat when a subpopulation of a metapopulation has gone locally extinct.

reserve See protected area.

reserve system A set of protected areas in a region, usually coordinated to conserve biodiversity of that region to some extent.

Resource Conservation Ethic A philosophical approach to conservation derived from the views of forester Gifford Pinchot, based on the utilitarian philosophy of John Stuart Mill. Nature is seen as a collection of natural resources, to be used for “the greatest good of the greatest number for the longest time.”

restoration or restoration ecology See ecological restoration.

risk assessment The process of identifying, evaluating and managing the risks that may arise from a given action or activity; e.g., the risk assessment of releasing a species as part of a biological control or a species reintroduction program.

Romantic-Transcendental Conservation Ethic A philosophical approach to conservation derived from the writings of Emerson, Thoreau, and Muir, in which nature is seen in a quasi-religious sense, and as having uses other than human economic gain. This ethic strives to preserve nature in a wild and pristine state.


The magnitude of a region or process. Refers to both spatial size—for example, a relatively small-scale patch or a relatively large-scale landscape; and temporal rate—for example, relatively rapid ecological succession or relatively slow evolutionary speciation.

secondary effects When the loss of population change in a species affects other species, often through their trophic interactions.

secondary extinctions Loss of a species as a direct or indirect result of the loss of another species.

selection Differential survival (viability selection) and reproduction (fertility selection) by different genotypes in the population or the differential success of genotypes passing gametes to other generations (sexual selection). See also natural selection.

sentient Capable of feeling or perception. Refers to a state of self-awareness among organisms, usually applied only to vertebrates.

simulated annealing A common method used in systematic conservation planning where a search for potential sites to include in a reserve system can include both optimal (good) and nonoptimal (bad) choices initially to achieve a better final result.

single gene traits Traits whose phenotype is largely controlled by a single gene. Usually falls into discrete or qualitative categories such as normal versus albino coat coloration.

sink habitat A habitat in which local mortality exceeds local reproductive success for a given species.

sink population A population in a low-quality habitat in which the birth rate is generally lower than the death rate and population density is maintained by immigrants from source populations.

SLOSS An acronym for “single large or several small,” reflecting a debate that raged for several years asking whether, all else being equal, it was better to have one large reserve or several small reserves of the same total size.

source and sink dynamics Spatial linkage of population dynamics such that high-quality habitats (sources) provide excess individuals that maintain population density, through migration, in low-quality habitats (sinks).

source habitat A habitat in which local reproductive success exceeds local mortality for a given species.

source population A population in a high-quality habitat in which the birth rate greatly exceeds the death rate and the excess individuals leave as emigrants.

spatial statistics A broad class of statistical models that are applied to data that have an explicit spatial distribution. See also geostatistics as a special subset.

spatially-explicit population model A population model, especially a simulation model, that takes space, differences in habitat quality, and inter-habitat movement into consideration.

speciation Any of the processes by which new species form.

species diversity Usually synonymous with “species richness,” but may also include the proportional distribution of species.

species invasion The rapid spread or population growth of a nonnative species into new areas.

species richness The number of species in a region, site, or sample. See also α-, β- and γ-richness.

stewardship Management of natural resources that conserves them for future generations. Usually used to distinguish from short-term, utilitarian management objectives.

steady-state economy An economy that has a constant stock of people and artifacts maintained at some desired sufficient levels by low rates of maintenance (or throughput). A steady state economy does not assume that continued economic growth, as measured by indicators like Gross Domestic Product (GDP), is prerequisite for sustainable development.

stochastic Random; specifically refers to any random process, such as mortality due to weather extremes.

substitute/alternative cost approach Estimates the market value of an environmental good by comparing it to a logical substitute that has an established market value. For example, in this approach the value of hunting a deer would be approximated by the value of an equivalent amount of purchased meat.

succession The natural, sequential change of species composition of a community in a given area.

supplementation Addition of individuals to an existing population of conspecifics. Sometimes called reinforcement.

supply The aggregate amount of goods or services available to satisfy economic needs or wants. The quantity of a good or service which producers are willing to sell at different prices. Supply involves the relationship between quantity and price.

surrogates One or more species selected as focal species for conservation planning with the intention that other species will also be conserved by the same efforts. Surrogate species are often ones with large-ranges, or sensitive to disturbance, or which have similar ecology to target species.

sustainable development In general, the attempts to meet economic objectives in ways that do not degrade the underlying environmental support system. Note that there is considerable debate over the meaning of this term. In Chapter 18, we define it as “human activities conducted in a manner that respects the intrinsic value of the natural world, the role of the natural world in human well-being, and the need for humans to live on the income from nature’s capital rather than the capital itself.”

synergism An interaction that has more than additive effects; for example, when the joint toxicity of two compounds is greater than their combined, independent toxicities.

systematic conservation planning The deliberate planning process of selecting sites to include in a reserve system using explicit criteria.


threatened species
Used internationally to refer to any species listed as Critically Endangered, Endangered, or Vulnerable according to the IUCN Red List of Threatened Species definitions. According to U.S. Federal law, a threatened species is a species that is likely to become endangered in the foreseeable future.

time preference The general desire to have goods and services sooner rather than later. The use of discounting allows future goods and services to be valued in present value thereby accounting for the bias of time preference.

total economic value (TEV) The sum of all use and nonuse values including both market and nonmarket.

tragedy of the commons An idea (set forth primarily by Garrett Hardin) that unregulated use of a common, public resource for private, personal gain will result in overexploitation and destruction of the resource.

translational scientist A natural or social scientist who can translate scientific language into a policy framework to enable decision-makers to use science effectively, and who can translate policy concerns into scientific questions so that scientists can address them.

translocation Management technique often used in mitigation for endangered species protection whereby an individual, population, or species is removed from its habitat to be established in another area of similar or identical habitat.

travel cost methodology Commonly used to evaluate recreational or conservation areas. Estimates how much people are willing to pay in travel and opportunity costs to visit a particular site, or to see a particular phenomenon (e.g., a wild Bald Eagle). It is part of the implicit market approach.


use value
All values except existence value.

utilitarian value See instrumental value.

utilitarian view A philosophical term applied to any activity that produces a product useful to humans, typically in some economic sense. Also used to describe a system of values which is measured by its contribution to human well-being, usually in terms of health and economic standard of living.

utility The difficult to measure sense of well-being. Economists generally use monetary terms as surrogate measures of utility. Also the “want-satisfying” power of goods; personal satisfaction received through an economic gain.


The process of a continuously distributed biota becoming separated by an intervening geographic event (such as mountain uplift or river flow), or extinction of intervening populations, resulting in subsequent independent histories of the fragmented biotas, and possible speciation events.

vulnerability threshold A population size or density below which a population becomes vulnerable to extinction. Used particularly to describe the phenomenon when risk of extinction rises sharply with only a small change in population size or number of habitat patches occupied.


The land area that drains into a stream; the watershed for a major river may encompass a number of smaller watersheds that ultimately combine at a common point.

wetlands Lands whose saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities that live in the soil and on its surface (e.g., Mangrove forests).

willingness to pay (WTP) Used in contingent valuation to estimate the value of a nonmarket good. WTP would generally be determined through questionnaires distributed to a representative population asking something like, “How much would you be willing to pay to protect a certain reserve or species?”


An important component of reserve design that controls human activities within and adjacent to conservation reserves, so that reserve function may be protected while some human activities, including those supplying some economic benefit, may take place.