The study assesses effects of population growth on agricultural land and forest in the Volta River Basin of Ghana. Most districts of the research area are experiencing shortfalls in land suitable for agriculture and deforestation. The number of farm holdings is decreasing and practice of fallow lands (last consequences of the former shifting cultivation) is also vanishing. Although households are wealthier due to new sources of off-farm income, the use of tractor, inorganic fertilizer and improved seed variety for farming is still low due to high costs. On deforestation, increases in fuel wood use and agricultural extensification are the major causes.

Coffea arabica, one of the economically most important crops worldwide, occurs naturally in the undergrowth of montane rainforests of Ethiopia. The study provides the first detailed ecophysiological investigations of wild coffee populations. It demonstrates the inter- and intra-regional variability in phenotypic and hydrological characteristics of wild coffee. The results reveal very different strategies of wild coffee seedlings for coping with drought stress. The ecophysiological diversity shows the importance of Ethiopian wild coffee populations as gene pools for future breeding programs, and underlines the need for an in-situ conservation strategy. The study includes recommendations for coffee forest management and the use of wild arabica coffee in Ethiopia.

Solanum quitoense (Lulo) from the northern Andes is a fruit with an attractive taste. It has a high export potential but its production is hampered by insufficient pollination. Studies on the reproductive system of Lulo revealed that, due to their poricidal anthers, the flowers need pollinators for self- and cross-pollination. Pollination by native bumblebees significantly increases fruit set and quality. Experiments show that colonies of Bombus atratus can be reared in captivity and used in Lulo fields for providing increased pollination services. Modeling based on data on colony development reveal larva/workers ratio and the supply of pollen as main parameters for improving the rearing method.

Plant biomass represents a sink for atmospheric carbon dioxide, which is one of the most important greenhouse gases and which is assumed to contribute more than half of the global warming. Establishing tree plantations or perennial crops on degraded land is an effective way to reduce atmospheric carbon by building up terrestrial carbon stocks, not only in the living biomass, but also in the soil. By converting Imperata cylindrica grassland into tree plantations (Acacia mangium or oil palm), aboveground biomass carbon can be increased about 20-fold and below ground biomass carbon up to 8-fold, while soil carbon can almost be doubled.