Biodiversity, ecosystems and ecosystem services

All ecosystems are shaped by people, directly or indirectly and all people, rich or poor, rural or urban, depend on the capacity of ecosystems to generate essential ecosystem services. In this sense, people and ecosystems are interdependent social-ecological systems. The ecosystem concept describes the interrelationships between living organisms (people included) and the non-living environment and provides a holistic approach to understanding the generation of services from an environment that both delivers benefits to and imposes costs on people. Variation in biological diversity relates to the operations of ecosystems in at least three ways: 1. increase in diversity often leads to an increase in productivity due to complementary traits among species for resource use, and productivity itself underpins many ecosystem services, 2. increased diversity leads to an increase in response diversity (range of traits related to how species within the same functional group respond to environmental drivers) resulting in less variability in functioning over time as environment changes, 3. idiosyncratic effects due to keystone species properties and unique trait-combinations which may result in a disproportional effect of losing one particular species compared to the effect of losing individual species at random. Ecosystems produce multiple services and these interact in complex ways, different services being interlinked, both negatively and positively. Delivery of many services will therefore vary in a correlated manner, but when an ecosystem is managed principally for the delivery of a single service (e.g. food production), other services are nearly always affected negatively. Ecosystems vary in their ability to buffer and adapt to both natural and anthropogenic changes as well as recover after changes (i.e. resilience). When subjected to severe change, ecosystems may cross thresholds and move into different and often less desirable ecological states or trajectories. A major challenge is how to design ecosystem management in ways that maintain resilience and avoids passing undesirable thresholds. There is clear evidence for a central role of biodiversity in the delivery of some – but not all - services, viewed individually. However, ecosystems need to be managed to deliver multiple services to sustain human well-being and also managed at the level of landscapes and seascapes in ways that avoid the passing of dangerous tipping-points. We can state with high certainty that maintaining functioning ecosystems capable of delivering multiple services requires a general approach to sustaining biodiversity, in the long-term also when a single service is the focus