Mapping a better future

Over much of Africa, farmers are planting tree seeds which aren't adapted to their land and climate.

A great store of information, drawn up by botanists working for the colonial authorities in Africa in the early 20th century, has been rescued from the archives, digitized and reinterpreted to provide farmers, non-governmental organizations (NGOs) and others with the guidance they need to plant the right trees in the right places. Let's say you want to rehabilitate an area of degraded land in Africa or plant large numbers of fruit or timber trees.

Where do you get information about which species to plant and where to get seeds and seedlings? The chances are you will have to rely on the knowledge of local organizations, nurseries or government extension staff. All too often, the advice will focus on a few favourite species which are not adapted to the local situation.

"Over much of Africa, farmers are planting tree seeds which aren't adapted to their land and climate," explains Jens-Peter Lillesø, a scientist with Forest and Landscape Denmark. He gives the example of Prunus africana, whose bark has important medicinal properties. Like many tree species, it consists of a large number of distinct populations, each of which is adapted to a particular set of ecological conditions. "You can't just collect seed from one place and expect to use it successfully in another," he says, "but that's what happens for most agroforestry species in Africa."

The Vegetation and Climate Change in East Africa (VECEA) project, described in our 2009-2010 annual report, has helped to provide a remedy in seven countries stretching from Ethiopia in the north to Zambia in the south. The vegetation maps produced by the project provide NGOs, farmers and tree seed centres with the information they need when choosing which trees to plant and where to source their seeds and seedlings. The project has also predicted which species will grow well, and where, under different climatic conditions.

During the past year, Roeland Kindt, an ecologist at the World Agroforestry Centre and collaborator in VECEA, conducted a parallel exercise to turn a vegetation map for the whole of Africa into a tree selection tool. The Useful Tree Species for Africa tool was funded by the United Nations Environment Programme and the Global Environment Fund as part of the Carbon Benefits Project. Kindt and his colleagues modified vegetation maps drawn up in 1983 by Frank White, an English botanist. These were based on maps made by botanists in earlier decades.

"We have turned White's map into a tool for selecting useful species, using an overlay on Google Earth," says Kindt. "It is interactive and easy to use. You click on the location you're interested in, and it provides information about the vegetation type, with links to species composition tables." Users can also select a subset of species to provide desired end-products or environmental services, and there are links to detailed descriptions of each tree species.

Inevitably, the resolution for the map of Africa – White used the scale of one to 5 000 000 – is lower than that used for the VECEA project. "Eventually, we would like to produce a map for the entire African continent which provides similar levels of detail and accuracy as VECEA," says Lilleso. "Nevertheless, the maps are still accurate enough to provide users with the sort of information they need to decide which agroforestry species will grow best in particular areas, and where to get their seeds and seedlings."