An environmental gradient, or climate gradient, is a change in

abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them under ...

(non-living) factors through space (or time). Environmental gradients can be related to factors such as

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

, depth,

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

, soil humidity and

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

. Often times, a multitude of biotic (living) factors are closely related to these gradients; as a result of a change in an environmental gradient, factors such as

species abundance In ecology, local abundance is the relative representation of a species in a particular ecosystem. It is usually measured as the number of individuals found per sample. The ratio of abundance of one species to one or multiple other species livin ...

, population density, morphology,

primary productivity In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...

, predation, and local adaptation may be impacted. Africa Precipitation Map

Abiotic Influence

The

species distribution Species distribution —or species dispersion — is the manner in which a biological taxon is spatially arranged. The geographic limits of a particular taxon's distribution is its range, often represented as shaded areas on a map. Patterns of ...

along environmental gradients has been studied intensively due to large databases of species presence data (e.g. GBIF). The abiotic factors that environmental gradients consist of can have a direct ramifications on organismal survival. Generally, organismal distribution is tied to those abiotic factors, but even an environmental gradient of one abiotic factor yields insight into how a species distribution might look. For example, aspects of the landscape such as soil composition, temperature, and precipitation all factor in to an accurate idea of habitable territory a plant species might occupy; information on one of those factors can help form an environmental gradient by which a proximate species distribution may be generated. Similarly, along the upstream-downstream gradient of a river, fish assemblages (groupings) can vary in species and trait diversity; upstream habitats, which tend to be at higher elevations, have been observed to develop greater species and trait diversity. With elevated regions most intensely feeling the effects of climate change and these effects being linked to increased species diversity in impacted regions, this is a key consideration in prioritizing habitats for conservation efforts. At an

ecotone An ecotone is a transition area between two biological communities, where two communities meet and integrate. It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and gras ...

, species abundances change relatively quickly compared to the environmental gradient.

Biotic Interactions

Although environmental gradients are comprised gradually changing and predictable patterns of an abiotic factor, there is strong interplay between both biotic-biotic factors as well as biotic-abiotic factors. For example, species abundances usually change along environmental gradients in a more or less predictive way. However, the species abundance along an environmental gradient is not only determined by the abiotic factor associated with the gradient but, also by the change in the

biotic interaction In ecology, a biological interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species (intraspecific interactions), or of different species (interspecific interaction ...

s, like

competition Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, ind ...

and predation, along the environmental gradient.

Local Adaptation Along Environmental Gradients

Depending on the size of the landscape and the

gene flow In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...

between populations, local adaptation could arise between populations inhabiting two extremes of the landscape. The opposing extremes in abiotic conditions that are faced between populations and the lack of homogenizing gene flow could present conditions where two populations are able to differentiate. Often times when comparing fitness or

phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological pr ...

values across an environmental gradient, the data are fixated into a reaction norm framework. In this way, an individual can directly assess the changes across a landscape of a particular species' phenotype or compare fitness and phenotypes of populations within a species across environmental gradients (particularly when performing reciprocal transplant studies).

Impact of Climate Change

Current models predict that as

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

intensifies, certain environmental gradients may experience the effects as changing rates of natural processes or impacts on distribution and characteristics of species within them. Given the interconnectedness of abiotic factors, long-term disturbances of one gradient have the possibility of affecting other gradients.

''Soil characteristics''

'' Soil respiration'', the process of soil naturally releasing carbon dioxide into the atmosphere, acts as an example of this. In areas where soil moisture is not limiting (with moisture being a key part of the respiration process), soil respiration increases with rising temperatures; thus, respiration patterns form the gradient, and higher emissions are observed in warmer ecosystems. Similarly, rate of precipitation has a positive correlation with respiration (as moisture no longer becomes a limiting factor). Thus, it not only is its own gradient (average precipitation across a range), but also connects with the respiration gradient and impacts it.

''Altitude''

Altitude gradients are a key consideration in understanding migration patterns due to the effects of global warming. As temperatures increase, trees adapted to warmer climates will migrate uphill for access to sunlight, and thus populations of temperate or cold-adapted trees and the habitats suitable for them will shrink.

Environmental gradients in society

Environmental gradients are not limited to naturally occurring variations in environmental factors across a range; they have also been created by human activity and industrialization. Air pollution is present as an environmental gradient in areas containing power plants, factories, and other pollutant-emitting facilities, as are environmental toxins, such as heavy metals, radiation, and pesticides; generally speaking, concentration decreases as distance from origin site increases. Differences in exposure to these elements across populations due to proximity to the origin site has become a major concern of environmental and public health activists, who cite health disparities linked to these gradients as an

environmental justice Environmental justice is a social movement to address the unfair exposure of poor and marginalized communities to harms from hazardous waste, resource extraction, and other land uses.Schlosberg, David. (2007) ''Defining Environmental Justi ...

concern.