Ecosystem transformation by climate change and its consequences for humans

The global climate and biodiversity crises are intimately linked. Climate extremes and their combinations with other global change factors are critical, yet uncertain drivers of changes in ecosystem biodiversity and functioning. Here, I summarise the diverse dynamics of ecosystems in response to climate extremes and their mechanisms. I then highlight the consequences of these responses for humans, and how changing biodiversity dynamics can be a resource for human adaptation to global environmental crises. Complex systems theory underpins key mechanisms of multiple types of ecosystem transformation: nonlinear responses and hysteresis, the interplay of fast and slow variables and the role of synergistic effects, cascading impacts and feedbacks. These dynamics are underpinned by biotic mechanisms involving biodiversity at all levels of organisation. Evidence on ecosystem transformation in response to climate extremes highlights that beyond their direct effects, climate extremes exacerbate other global change factors of the biodiversity crisis. Then, by altering ecosystem structure, biodiversity and functioning, climate change impacts the whole range of nature’s contributions to people, and decreases functions underpinning adaptation and mitigation. There is increasing scientific and operational evidence that ecosystems in good condition are however critical to adaptation to climate change. Nature’s contributions to adaptation comprise climate change and risk mitigation, the resilience and transformative ability of biodiverse and spatially connected ecosystems, along with the social construction of new values for transformed ecosystems. Processes of nature-based adaptation require a transformation in the production and sharing of knowledge of relevant ecological processes, in values for nature and in social relations.