The geometry of preserves: Determining the trade-off between preserves and land-use intensity


With an ever increasing population on Earth, there is more demand and pressure placed on the land and its resources to help support this growth. This comes at the cost of habitat for many species, which no longer have the necessary resources to survive. While some of this can be remedied by creating reserves on which these animals can live, the result is that the land surrounding such reserves may have more intense usage. As a result, many conservationists have tried to determine the optimal balance between the amount of habitat protected relative to the surrounding area available for human consumption in an effort to find a compromise between humans and species protection. What has been less frequently studied is how land-use intensity surrounding protected areas affects the species richness within these areas. Researchers at the University of Wisconsin-Madison, in conjunction with researchers at Humboldt University in Berlin, recently published a paper which develops analyses to look at this interaction, and found that the size of protected areas required to achieve the goal of conservation depends heavily on how much of an impact land-use surrounding the preserve is expected to have.

Previous studies have suggested that large protected areas surrounded by high intensity land use were the best solution. However, none of these studies took into account the interaction between the land used outside and protected area inside. The recent study, conducted by Butsic et al. and published in the journal Conservation Biology, found that the interaction between land usage outside a protected area and the level of species richness inside can be very much influenced by the intensity with which the surrounding land is used. They reported that when this consideration is included in calculations, large protected areas and high intensity land usage is never the optimal solution. This could potentially affect policy regarding protected reserves, by altering the size and the distribution of such areas.

Butsic et al. created several models to examine the effect interaction between land usage and species richness within protected areas had, depending on intensity of land usage. The researchers found that if species richness responded to an increase in intensity of land usage due to protection of large areas, an increase in protected area would lead to a decrease in species richness because of increased land use in the surrounding area. In some instances, it was better to have no protected areas and use all of the land at a low intensity, and in other instances, the best solution was a mixture of both protected and unprotected areas. However, assuming this interaction takes place, the optimal solution was never a single, large protected area.

While the authors stress that the results are limited by the assumption of a homogenous habitat, as well as the lack of accounting for non-native species which often follow human intervention in habitats, the finds suggest that the planning of protected areas and reserves must take into account how the land surrounding the reserve will be utilized. This could change not only the shapes and sizes of protected areas, but also their distribution. The problem, the authors say, is that few protected areas have the staff or resources to attend to land usage outside the protected area, a variable which could have a very significant impact on the success of the reserve in maintaining species richness. Despite this, the knowledge that the intensity of land usage surrounding protected areas is important in determining species richness allows this consideration to be taken into account and could potentially help promote species richness in future reserves.



Butsic V, Radeloff VC, Kuemmerle T, and AM Pidgeon. 2012. Analytical solutions to trade-offs between size of protected areas and land-use intensity. Conservation Biology. 26: 883-893.  


Photo: Allen J and Simmon R. NASA Earth Observatory. <;

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