Post submitted by Andrew Jacobson.
What do you think of when you hear the words “remote sensing?” Or what about “wildlife corridors?” While both of these remain somewhat esoteric concepts, they share an important link. Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object1, in this case the earth from satellites or aircraft. A wildlife corridor is an area of habitat connecting wildlife populations separated by human activities or structures2. As it turns out, remote sensing is often essential for identifying wildlife corridors (often linked via animal tracking). An essential first step in working out where lions and other big carnivores are likely to survive, or traverse, is the accurate identification of the distribution and extent of human converted land cover (such as cities and croplands). However, even with remote sensing, this task can be quite difficult.
In light of the difficulty of obtaining accurate land cover maps, particularly in developing countries; researchers with National Geographic’s Big Cats Initiative designed a new open-access web application, GE Grids3. This tool is the first of its kind, allowing users to create land use land cover maps for free using high-resolution satellite imagery available on Google Earth. Researchers applied GE Grids to identify the distribution of human converted land cover across East Africa.
The researchers discovered that nearly 30% of East Africa (Kenya, Tanzania, Uganda, Rwanda and Burundi) is converted to human land cover. Most dramatically, over 80% of densely populated Rwanda and Burundi are occupied by humans, leaving little room for wildlife. On the other hand, slightly more than 80% of Kenya remains in a natural state. Tanzania, a country with the world’s largest population of African lions (Panthera leo) and one of the largest populations of African elephants (Loxodonta africana) is roughly 1/3rd converted to human land use.
While roughly 2/3rds of Tanzania remains primarily in natural land cover, the distribution and pattern of the 1/3rd of human-dominated land is important. Hence, this new map can assist in identifying remaining patches of large carnivore habitat and wildlife corridors. More on this is forthcoming.
Yet new research with collaborators from the Tanzania Wildlife Research Institute showcases how this data is already being used4. African wild dogs (Lycaon pictus) are an endangered large carnivore native to Africa. While superficially similar to domestic dogs, our pets are descendants of wolves, not this species. Some radio-collared African wild dogs were recently tracked dispersing from where they were born in Tanzania. One pack was tracked moving nearly 4000 km, or a straight-line distance of just over 500 km (4000 km is roughly the distance between London and the east coast of Canada). This is the farthest dispersal distance yet recorded for this species. Despite their extensive explorations, very little of their movement was in human-dominated landscapes (see video).
With this improved map of human land cover in hand, next steps will be to suss out how and why large carnivores navigate around these areas, or occasionally cross them.
The GE Grids tool is licensed under the creative commons and can be downloaded here.
- Schowengerdt, Robert A. 2007. Remote sensing: models and methods for image processing (3rd edition). Academic Press. ISBN 978-0-12-369407-2.
- Beier, P., D. Majka, J. Jeness. 2006. Conceptual steps for designing wildlife corridors.
- Jacobson, A., J. Dhanota, J. Godfrey, H. Jacobson, Z. Rossman, A. Stanish, H. Walker and J. Riggio. 2015. A novel approach to mapping land conversion using Google Earth with an application to East Africa. Environmental Modelling and Software: doi:10.1016/j.envsoft.2015.06.011
- Masenga, E., C. Jackson, E. Mijingo, A. Jacobson, J. Riggio, R. Lyamuya, R. Fyumagwa, and E. Røskaft. Insights into long-distance dispersal by African wild dogs in East Africa. African Journal of Ecology: doi:10.1111/aje.12244