5. Trade-off between different ecosystem services

Land use change may result in the increase in some ecosystem services but at the same time the reduction in other services. Such trade-offs always occur when management practices are oriented towards the production or use of a given ecosystem service, without taking into account the consequences for other services [23]. For example, the more forest that is transformed, services provided by plant-dominated ecosystems such as farmlands or pasture lands increase, with the production of agricultural and pastoral goods being increased, whereas the services provided by the tree-dominated forests decline. For example, Leh et al. [42] used InVEST model (Integrated Valuation of Ecosystem Services and Tradeoffs) to quantify the spatial pattern of ecosystem services including biodiversity, surface water yield, carbon storage, sediment retention, nitrogen retention, and phosphorous retention in the tropical African countries Ghana and Cote d'Ivoire. The land use scenarios from 2000 to 2005 and 2009 were used to analyze the change in those ecosystem services. By employing this tool, it is possible to quantitatively understand the change in ecosystem services at different spatial scales and thus makes the planning of land use strategy possible. The results of Leh et al.'s work emphasize the great challenges that we face to maintain ecosystem services provided by tropical forests, while land use change processes are becoming increasingly more important.

Another example of these complex trade-offs is the effect of land use change on freshwater availability when transforming tropical forests into other type of ecosystem. In theory, grasses and shrubs use less water than trees, having therefore lower evapotranspiration rates (Oliveira et al. this volume). This could lead to higher runoff and increased provision of water downstream [23]. However, clearing tropical forests also reduces infiltration rates, increasing erosion, soil evaporation, and runoff, which in turn can lead to reduction in water quality and decrease in water recharge rates (see above). The importance of trade-offs also appears when considering that ecosystem services also depend on the users: different stake holders value different services in different ways, and therefore, it is difficult to objectively determine whether a land use change is diminishing or increasing the provisioning of ecosystem services. It would depend on who is asked [23].
