As habitat fragmentation continues to impact landscapes globally, conservation decisions often focus around maintaining large patches of native vegetation. Based on island biogeography theory, bigger patches should be more important, with higher species richness and larger, more robust populations. Bigger, more connected patches are thus often given priority over smaller patches.
The consequence is that conservation policies across many countries allow small, isolated patches to be poorly managed, or even eliminated. Many policies are implemented without considering how these patches may complement existing reserves or support underrepresented habitats. Small, isolated patches have the potential to support ecological communities that are unique and less well represented in existing conservation areas, making them more valuable than they first appear.
New research examines the potential benefit of conserving small, isolated patches based on the principles of complementarity and representativeness. A global analysis of 31 spatial conservation case studies in 27 countries across North America, Africa, Australia, and Europe provides the foundation for testing the relationship between patch size, isolation, shape, and conservation value.
Results from the analysis show that small, relatively isolated patches with high shape complexity have higher conservation value than similar sized patches that are more connected with low shape complexity. For example, a 1 hectare parcel of land from a small, complex patch surrounded by low-quality matrix has a higher conservation value than a similar parcel of land from a large, intact landscape. In several case studies, small, isolated patches represented some of the last strongholds for many rare and threatened animals and plants.
The main message is that small patches, while not necessarily a top priority, should no longer be given no priority. They potentially contain species that are found nowhere else in other protected areas, and can complement the species richness found in larger patches. These small patches may contain irreplaceable biodiversity, and should not be ignored in conservation planning and policy making.
Wintle, B.A., Kujala, H., Whitehead, A., Cameron, A., Veloz, S., Kukkala, A., Moilanen, A., Gordon, A., Lentini, P.E., Cadenhead, N.C. and Bekessy, S.A. 2019. Global synthesis of conservation studies reveals the importance of small habitat patches for biodiversity. Proceedings of the National Academy of Sciences 116(3): 909-14.