Global biodiversity scenarios and landscape ecology

The composition of ecological communities is both cause and consequence of landscape pattern. Predicting biodiversity change involves understanding not only ecology and evolution, but also complex changes in human societies and economies. Scenarios offer a less rigid approach to thinking about biodiversity change in a policy and management context. They shift the focus of research and management from making singular predictions and developing single 'best' strategies to exploring uncertainties and assessing the outcomes of alternative policies. The four Millennium Ecosystem Assessment (MA) biodiversity scenarios illustrate current approaches to biodiversity estimation in global scenarios. The MA biodiversity scenarios are built around the species-area relationship and the magnitudes of a few area-dependent processes such as nitrogen deposition and climate change. Some of the most obvious landscape-related omissions from the MA scenarios are pattern-process feedbacks, scale dependencies, and the role of landscape configuration. While the MA has set a new standard for biodiversity scenarios, future exercises would benefit from a more multi-scale and more mechanistic framework. I use examples from research on the landscape ecology and biogeography of African ticks to illustrate how a hypothesis-based approach can be used to analyse the multi-scale, multi-level drivers of change in patterns of species occurrences. Two of the most important challenges for the future development of both landscape ecology and biodiversity scenarios are to become more mechanistic (less pattern-based) and more general (applicable across different landscapes).