What is the species–area relationship in simple terms?

The larger the area you survey, the more species you find, and the increase follows a regular mathematical rule. Roughly, ten times the area gives about twice the species.

Why does it matter for conservation?

It is used to think about the size and design of reserves and to estimate how many species habitat loss might eliminate, though it can overestimate extinction rates.

Species–Area Relationship

🔬 Natural Sciences By CampusDown Wiki Editorial Team Last updated October 26, 2026

The species–area relationship is the empirical rule in ecology that the number of species found in a region increases as the area surveyed grows. It is usually expressed as a power function, S = cA^z, where S is the number of species, A is area and z typically lies between about 0.15 and 0.35. The Swedish scientist Olof Arrhenius (1921) first proposed this form.

Contents

1. Origins and basic form
2. Theoretical explanations and island biogeography
3. Conservation applications and limits
4. FAQ
5. References

Origins and basic form

The nineteenth-century British botanist Hewett Watson (1859), compiling lists of British plants, recorded that larger areas contain more species. Olof Arrhenius (1921) expressed this as the power function S = cA^z, while Gleason (1922) proposed an alternative model in which species number is proportional to the logarithm of area. Taking logarithms of both sides of the power form gives a straight line, so the slope z describes how quickly species number rises with area. A commonly used rule of thumb is that a tenfold increase in area roughly doubles the number of species. The relationship is a classic biological example of a power law.

Theoretical explanations and island biogeography

Preston (1962) proposed the canonical distribution theory, showing that if species abundances follow a lognormal distribution, the z-value of the species–area curve is about 0.26. MacArthur and Wilson's (1967) theory of island biogeography held that the number of species on an island is set by a balance between immigration of new species and extinction of existing ones, and that larger islands have lower extinction rates and so sustain more species. Connor and McCoy (1979) distinguished habitat diversity, sampling effects and immigration–extinction balance as causes of the relationship and set out the statistical issues involved. Rosenzweig (1995) synthesized evidence that the shape and slope of the curve change with spatial scale.

Conservation applications and limits

Drawing on the species–area relationship, Diamond (1975) proposed the design principle that a single large reserve is better than several small ones, and Simberloff and Abele (1976) countered that this need not be so, starting what became known as the SLOSS debate. Pimm et al. (1995) and Thomas et al. (2004) used the relationship to estimate future extinctions from habitat loss and climate change. He and Hubbell (2011), however, argued that applying the species–area curve in reverse overestimates extinction rates from habitat loss. Triantis, Guilhaumon and Whittaker (2012) compared which mathematical models best fit island data, addressing both biological interpretation and statistical model choice.

FAQ

What is the species–area relationship in simple terms?: The larger the area you survey, the more species you find, and the increase follows a regular mathematical rule. Roughly, ten times the area gives about twice the species.
Why does it matter for conservation?: It is used to think about the size and design of reserves and to estimate how many species habitat loss might eliminate, though it can overestimate extinction rates.

Sources reviewed: 2026-10-26

References

Arrhenius, O. (1921). Species and area. Journal of Ecology, 9(1), 95–99.
Gleason, H. A. (1922). On the relation between species and area. Ecology, 3(2), 158–162.
Watson, H. C. (1859). Cybele Britannica (Vol. 4). London: Longman.
Preston, F. W. (1962). The canonical distribution of commonness and rarity: Part I. Ecology, 43(2), 185–215.
MacArthur, R. H., & Wilson, E. O. (1967). The Theory of Island Biogeography. Princeton: Princeton University Press.
Connor, E. F., & McCoy, E. D. (1979). The statistics and biology of the species–area relationship. American Naturalist, 113(6), 791–833.
Diamond, J. M. (1975). The island dilemma: Lessons of modern biogeographic studies for the design of natural reserves. Biological Conservation, 7(2), 129–146.
Simberloff, D. S., & Abele, L. G. (1976). Island biogeography theory and conservation practice. Science, 191(4224), 285–286.
Rosenzweig, M. L. (1995). Species Diversity in Space and Time. Cambridge: Cambridge University Press.
Pimm, S. L., Russell, G. J., Gittleman, J. L., & Brooks, T. M. (1995). The future of biodiversity. Science, 269(5222), 347–350.
Thomas, C. D., et al. (2004). Extinction risk from climate change. Nature, 427(6970), 145–148.
He, F., & Hubbell, S. P. (2011). Species–area relationships always overestimate extinction rates from habitat loss. Nature, 473(7347), 368–371.
Triantis, K. A., Guilhaumon, F., & Whittaker, R. J. (2012). The island species–area relationship: Biology and statistics. Journal of Biogeography, 39(2), 215–231.

Reports and materials that use this theory (Korean)

There are no materials dedicated to this theory yet, but you can search related reports in the CampusDown library (Korean).

Find more reports · Search '종-면적 관계' on CampusDown →

Island BiogeographyWhat the theory of island biogeography is: species richness set by a balance of immigration and extinction, more species on larger and nearer islands, species–area curves, the mangrove experiments and conservation uses.🔬 Natural Sciences MetapopulationWhat a metapopulation is: a population of local populations linked by dispersal, its origins, the Levins model and equilibrium occupancy, Hanski's incidence function model, fragmentation, extinction debt and metacommunities.🔬 Natural Sciences Power LawWhat a power law is, Pareto's income distribution and Zipf's law of word frequency, examples from earthquakes, cities, citations and networks, how fat tails differ from the normal distribution, generating mechanisms, and the statistical testing debate.➗ Mathematics & Statistics Island RuleWhat the island rule is: the tendency of large animals to shrink and small animals to grow larger on islands, Foster's 1964 observations, fossil cases of dwarfism, ecological explanations based on resources, predation and competition, and meta-analyses.🔬 Natural Sciences Intermediate Disturbance HypothesisWhat the intermediate disturbance hypothesis is: why diversity may peak at moderate disturbance, Connell's formulation, succession and competitive exclusion, Sousa's experiments, Huston's model, meta-analyses and Fox's call to abandon it.🔬 Natural Sciences

Latest ArticlesView all ›

New guides for college study and assignments (Korean)

This article was last updated on October 26, 2026. It is based on widely recognized original works and textbooks; when citing it in a paper, please check the original sources listed in the references.