Climate change and ecosystems: threats, opportunities and solutions
The rapid anthropogenic climate change that is being experienced in the early twenty-first century is intimately entwined with the health and functioning of the biosphere. Climate change is impacting ecosystems through changes in mean conditions and in climate variability, coupled with other associated changes such as increased ocean acidification and atmospheric carbon dioxide concentrations. It also interacts with other pressures on ecosystems, including degradation, defaunation and fragmentation. There is a need to understand the ecological dynamics of these climate impacts, to identify hotspots of vulnerability and resilience and to identify management interventions that may assist biosphere resilience to climate change. At the same time, ecosystems can also assist in the mitigation of, and adaptation to, climate change. The mechanisms, potential and limits of such nature-based solutions to climate change need to be explored and quantified. This paper introduces a thematic issue dedicated to the interaction between climate change and the biosphere. It explores novel perspectives on how ecosystems respond to climate change, how ecosystem resilience can be enhanced and how ecosystems can assist in addressing the challenge of a changing climate. It draws on a Royal Society-National Academy of Sciences Forum held in Washington DC in November 2018, where these themes and issues were discussed. We conclude by identifying some priorities for academic research and practical implementation, in order to maximize the potential for maintaining a diverse, resilient and well-functioning biosphere under the challenging conditions of the twenty-first century.
Changes in the atmosphere and oceans can profoundly change the biosphere, the thin living film of life on Earth that is intrinsically coupled to the atmosphere and hydrosphere and provides the nourishing fabric within which human societies exist. Hence, degradation or restoration of parts of the biosphere are likely to have regional or planetary consequences. Anthropogenic greenhouse gas emissions, which drive both climate change and ocean acidification, increasingly threaten the viability and resilience of natural ecosystems, and the human societies that depend upon them. The effects of these threats can be profound and, in recent years, have become increasingly observable. Already, Earth is committed to a substantially warmed climate, with expectations of further warming into the future, unless carbon emissions trajectories change dramatically
Scientific research continues to refine the understanding of Earth's climate system and its interdependence on the biosphere. For the most part, projections indicate an increased likelihood of negative consequences of climate change for ecosystems and people. Indeed, climate-related impacts are already being witnessed and seem to be increasing in severity and frequency. A number of potential climate tipping points in the Earth system are already showing early signs of activation [2]. Consequently, the 2018 International Panel on Climate Change (IPCC) Special Report on 1.5°C (https://www.ipcc.ch/sr15/) warns that allowing the planet to warm beyond 1.5°C will result in climate change impacts, including drought, floods, heat waves and sea-level rise, that are deleterious for humanity and for biodiversity. While the previous internationally agreed target was 2°C, this half-degree difference could reduce the risk of extensive degradation of Arctic and coral reef ecosystems. A 1.5°C maximum warming ambition implies that the world has about 12 years to reduce global net carbon emissions by half to avoid the most significant impacts, but even if this target is achieved, potential impacts of warming are likely to continue for decades or even centuries [3].
In this thematic issue, we present contributions that culminate from discussions held at the 2018 Royal Society-National Academy of Sciences Forum on Climate Change and Ecosystems. The aims of the Forum, jointly organized by the two societies, were to build new opportunities for international collaboration, highlight the latest research findings on the focal topic, identify research gaps and future research priorities and discuss how research in this field may inform international policy [4]. The Forum examined the latest science on how climate change can affect terrestrial, aquatic and marine ecosystems, often in interaction with other factors. In particular, it addressed research frontiers such as the effects of changes in climate variability and extremes; interactions among multiple stressors; thresholds and the potential for abrupt change; and multi-trophic interactions, across a range of terrestrial, aquatic and marine ecosystems. The Forum also considered opportunities to assist and manage ecosystems to enhance both their resilience and societal resilience to climate change by exploring a range of science and policy dimensions. This included how ecosystems can best be managed to enhance their resilience to climate change, their ability to transform under climate change and how ecosystem management can be a strategy for more general adaptation to change. Hence, a central focus was to consider how ecosystem management and restoration have the potential to contribute ‘nature-based solutions’ (NbS) to tackle both the causes and consequences of climate change. However, the effectiveness, scalability and magnitude of different nature-based strategies need to be explored, better understood and evaluated [5].