What's a wildlife corridor?

Ecological corridors are routes that facilitate the free movement of animal life - be it a river linking fresh and saltwater habitats, or a man-made bridge built to minimise roadside fatalities. Nina Bhola is an ecologist from the UN Environment Programme World Conservation Monitoring Centre here in Cambridge, who looks at ways to manage land for the benefit of human development and biodiversity, and this corridor concept is important in the work she does. Phil Sansom and Katie Haylor spoke to Nina...

Nina - Ecological corridors are clearly defined areas that are managed for the long term to maintain or restore connectivity between protected areas and natural areas. They could be on land, freshwater, and marine ecosystems, or even in the air. They can be managed from small scales, to regional scales, to even continental scale; so thinking about ecological corridors that are managed to support migratory turtles or birds. There's clear guidance; it's been developed to support restoring and managing these corridors; and they take various forms. They could be from crossings built by people like bridges or tunnels to help wildlife cross safely. The routes could also be used by wildlife seasonally to reach water or food; for example, the movement of 1.5 million wildebeest migrating across the protected Mara Serengeti ecosystem that straddles the border between Kenya and Tanzania, for example. And it often takes many years for these animals to learn where to move in order to find food, and this behaviour is generally passed from generation to generation.

Phil - You've mentioned a lot of different types of corridors. Are they a particularly important concept, Nina?

Nina - Yes, it's a very important concept that planners and developers need to take into account. We're looking at our environment now today: human development has altered the natural areas in a variety of ways, causing these areas to become somewhat disconnected or fragmented. This has a really big impact on the movement of species and ultimately on their survival. There may be barriers that hinder this movement, like linear infrastructure such as roads or railways, or even fences that cut right through areas in which animals naturally move. The science shows that maintaining ecological corridors through connectivity conservation is essential for keeping species, populations, and ecosystems viable; and without connectivity, these ecosystems can't function properly, and without well-functioning ecosystems, biodiversity or nature is at risk. And when we talk about biodiversity, we're thinking about the variety of all life on earth, which actually underpins our lives: from the production of food, to clean water, to the health of our global economy. And we know that today the world is facing a global nature crisis, with up to almost a million species are now known to be threatened by extinction.

Katie - Nina, specifically you've been looking at how best to manage movement priorities between people and elephants in Kenya, haven't you? Tell us a bit about your project.

Nina - We have a project called the development corridor partnership, and the overarching aim of the project is really to investigate how human infrastructure impacts on animal movement, and to understand what we can do to minimise that impact. And so one specific element of the project looks at the ongoing phased development of an extensive railroad network, which is affecting the movement of elephants crossing between protected areas and their natural habitats in search of food. And really this first phase of the railway has established underpasses for animals; some parts of the railway have also been elevated to around 15 metres to allow elephants to move under; but we need to do a better job at understanding how these animals respond to these structures, especially as we know it takes a long time for them to recognise them, for them to know where the crossings are in the first place.

Katie - How much do we understand about the impact that climate change is having, or is likely to have, on animal movement? Because presumably, if the way animals move changes, then the way that land needs to be managed could change.

Nina - Absolutely. Climate change has real implications for wildlife corridors, because climate change can change the patterns of animal movements. Animals generally need to move in response to food availability, and when climate changes, with increasing droughts, it's just going to make it more and more difficult for animals to find this food. And that's why scientific data and modelling is so important. We need to be able to predict how animal movements might change in the future and plan accordingly. And this is also true for people: people are moving as climate change occurs. With this increasing human alteration, we need to think, and we need to act, at larger spatial scales, and therefore both planning and management need to consider well-designed ecological corridors that benefit both people and nature.

Katie - So what are the next steps for your Kenyan project?

Nina - It's really about the learnings: using science, using spatial models and maps, can actually help us to identify where animals cross. These results will be very useful to help inform a future phase that is being carried out to develop the third part of the railway network. And we've seen lots of successes in many parts of the world in both avoiding infrastructure, especially in highly sensitive areas. And so the results from this project have enormous potential to help planners and decision makers think about where future ecological corridors could be placed to help wildlife cross safely and protect vital landscapes.