Editor’s Choice 57:09 – Multi-species connectivity in a trans-frontier conservation landscape

As the September Editor’s Choice for Journal of Applied Ecology, research from Angela Brennan and colleagues moves away from a single-species approach and instead looks at movement corridors and connectivity on a large scale and across multiple species. Associate Editor, Kulbhushansingh Suryawanshi shares the important impact this could have on future conservation and development plans.

As our human footprint continues to grow and spread around the planet, the matrix of human-use areas that separate areas of conservation importance is becoming more and more hostile for large mammals. Therefore, maintaining connectivity between protected areas by building strategic corridors has become imperative, or else protected areas will exist as islands within an ocean of unsuitable habitats.

Connectivity within a landscape is important for maintaining ecological processes such as migration of species and gene flow, which are necessary for ecosystem function and climate resilience. However, work on corridors and connectivity conservation so far has largely focused on single species. This may not be representative of the entire suite of large mammal species that occur in those protected areas.

Elephants have often been the focus of connectivity studies but Brennan et al. find wild dogs and hyaena to provide important insights. Photo: Angela Brennan

In their Editor’s Choice research, Angela Brennan and her team try something novel and big at the same time. They used radio collar data on the movement of six species of large mammals (African elephant, lion, spotted hyaena, African wild dog, African buffalo and roan antelope) and applied circuit theory to assess connectivity in an important conservation landscape which is over 500,000 km2. Their study area is larger than 143 of the 194 countries in the world; or nearly as big as Spain! Furthermore, their study area spans across five countries: Angola, Botswana, Namibia, Zambia and Zimbabwe.

In this large landscape, the authors examine omni-directional wall to wall connectivity, which means, they imagine every pixel in this landscape to be a resistor with a cost to moving through it. Just as electricity moves through a grid, animals move through this landscape from any one point to another using the least cost path. With this approach the authors are able to identify areas within the landscape which are blocked off by barriers, or areas which are pinch points for a lot of animal movement. Together, this makes the study one of the most comprehensive work on connectivity conservation.

Veterinary fence in Namibia’s Bwabwata National Park. Photo: Angela Brennan

Unsurprisingly, the authors find that fences and roads pose a major barrier for animal movements. Veterinary fences and border fences between countries cut off elephant populations almost completely. The study finds that elephants in Botswana may be completely cut off from all other elephant populations in the region. Ironically, such isolation can inflate the densities of elephants locally, causing unusually large impacts on the habitat. The study also found roads and areas of high human use to be important barriers to animal movement. Their multi-species approach suggests that these barriers are not species specific and apply to almost all wildlife.

Traditionally, elephants have been the species of choice for studies in connectivity. Brennan and team, however, find that spotted hyaena and African wild dogs are perhaps better surrogates to assess connectivity in conservation landscapes of Africa. A focussed assessment of elephant corridors did reveal their use as multi-species hotspots, typically as pinch points between large fences. A multi-species assessment of connectivity clearly offers far better insights than single species.

The approach developed by Dr. Brennan and the team has multiple applications for conservation. This approach can be used to examine potential impacts of future development plans on connectivity conservation in a region. Using this approach, one can predict the impact of a road or a fence being proposed. Not only will we understand the potential impact of the proposed road or fence, but also the effect on the movement potential of the entire landscape. Furthermore, this approach can also be used to evaluate potential restoration measures to mitigate the impacts of existing barriers as well as potential future barriers. This approach is also valuable in removing existing barriers whose persistence is of low value to human use and whose removal is of high value for connectivity conservation. Most importantly, this study highlights that assessing connectivity with multiple species is a better approach to prioritising areas for conservation in a landscape.

The full Editor’s Choice article, Characterizing multispecies connectivity across a transfrontier conservation landscape, is free to read for a limited time in Journal of Applied Ecology.

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