Globally, 60% of the evaporation from land returns as precipitation over land and a fifth of annual precipitation over land is directly dependent on the presence of vegetation-supplied moisture. In many regions, particularly in dry seasons, a majority of the precipitation relies on moisture from vegetation and is therefore vulnerable to changes in upwind land use that modify water moisture supply to the atmosphere. The benefits of precipitation for societies are invaluable, ranging from food production to carbon sequestration, and the role of ecosystems for supplying moisture for rainfall can be therefore be considered an important, albeit under-appreciated, ecosystem service.   Our research shows that loss of moisture-supplying ecosystems, such as deforestation in the Amazon, can disrupt such moisture supplies, thereby reducing precipitation and negatively impacting crop yield, wetlands, and forest resilience in downwind regions. Conversely, some human activities, such as afforestation and irrigation, bring untapped subsoil water resources into the atmosphere and can help mitigate dry spells both locally and remotely. While they can have the potential to bring moisture-supplying benefits similar to moisture-supplying ecosystems, they also carry the risk of depleting local surface and groundwater resources and bringing about other adverse trade-offs.  The past decade has seen rapid developments in moisture tracking models and data, which have brought to light previously ignored long-distance moisture flow relationships among different land areas, land users, and land-use decisions. These scientific advances mean that it is now possible to map out the ecosystem service of vegetation-supplied precipitation at a global scale in great detail, as well as to track their dependencies and interdependencies.  We argue that the time is ripe for moisture-supplying ecosystems to be widely considered in land management and governance contexts. Nevertheless, a few important challenges remain. Particularly, future research needs to better constrain the uncertainties of moisture recycling relationships under climate change and atmospheric circulation change; to understand the effects of ecosystem adaptation, regime shifts, and social-ecological feedbacks; as well as to quantify the multiple benefits and trade-offs of the ecosystem service of vegetation-supplied precipitation. A better understanding of the relationships between moisture supply, drought mitigation, ecosystem resilience, and terrestrial carbon is especially relevant under the current UN Decade of Ecosystem Restoration as well as for achieving the Paris Agreement temperature target.
Ecosystem management that attempts to maximize the production of one ecosystem service often results in substantial declines in the provision of other ecosystem services. For this reason, recent studies have called for increased attention to development of a theoretical understanding behind the relationships among ecosystem services. Here, we review the literature on ecosystem services and propose a typology of relationships between ecosystem services based on the role of drivers and the interactions between services. We use this typology to develop three propositions to help drive ecological science towards a better understanding of the relationships among multiple ecosystem services. Research which aims to understand the relationships among multiple ecosystem services and the mechanisms behind these relationships will improve our ability to sustainably manage landscapes to provide multiple ecosystem services.
Over the past 50 years, a large number of development initiatives have addressed the diverse social and ecological challenges in the Sahel, often focusing on a single entry point or action, resulting in only a limited degree of success. Within the last decade, the international development discourse has evolved to incorporate resilience thinking as a way to address more complex challenges. However, concrete examples as to how to operationalize resilience thinking are lacking. The Great Green Wall for the Sahara and the Sahel Initiative (GGW), a pan-African program with a strong reforestation focus, is the latest and most ambitious of these development programs to date. The GGW represents an ideal opportunity to apply resilience thinking at a large scale, but in order to do so, it must intelligently gather and centralize pre-existing interdisciplinary knowledge, generate new knowledge, and integrate knowledge systems to appropriately navigate future uncertainties of the diverse social-ecological systems along its path. Herein, after a brief description of large-scale reforestation history in the Sahara and Sahel and the conceptual evolution of the GGW, we propose a transdisciplinary research framework with resilience thinking at its core. It includes analysis of complex social-ecological systems, their temporal and spatial cross-scale interactions, and outcomes focused on the supply of abundant, diverse, equitable, and durable ecosystem services to support livelihoods in the region. If the research areas that comprise the framework were to be properly addressed, they could conceivably guide GGW actions in a way that would contribute to desirable future pathways.
In Molden, David (Ed.). Water for food, water for life: a Comprehensive Assessment of Water Management in Agriculture. London, UK: Earthscan; Colombo, Sri Lanka: International Water Management Institute (IWMI).
Abstract Homo sapiens is currently living in serious disharmony with the rest of the natural world. For our species to survive, and for our well-being, we must gather knowledge from multiple perspectives and actively engage in studies of planetary health. The enormous diversity of species, one of the most striking aspects of life on our planet, provides a source of solutions that have been developed through evolution by natural selection by animals living in extreme environments. The food system is central to finding solutions; our current global eating patterns have a negative impact on human health, driven climate change and loss of biodiversity. We propose that the use of solutions derived from nature, an approach termed biomimetics, could mitigate the effects of a changing climate on planetary health as well as human health. For example, activation of the transcription factor Nrf2 may play a role in protecting animals living in extreme environments, or animals exposed to heat stress, pollution and pesticides. In order to meet these challenges, we call for the creation of novel interdisciplinary planetary health research teams.
An ecosystem service is a benefit derived by humanity that can be traced back to an ecological process. Although ecosystem services related to surface water have been thoroughly described, the relationship between atmospheric water and ecosystem services has been mostly neglected, and perhaps misunderstood. Recent advances in land-atmosphere modeling have revealed the importance of terrestrial ecosystems for moisture recycling. In this paper, we analyze the extent to which vegetation sustains the supply of atmospheric moisture and precipitation for downwind beneficiaries, globally. We simulate land-surface evaporation with a global hydrology model and track changes to moisture recycling using an atmospheric moisture budget model, and we define vegetation-regulated moisture recycling as the difference in moisture recycling between current vegetation and a hypothetical desert world. Our results show that nearly a fifth of annual average precipitation falling on land is from vegetation-regulated moisture recycling, but the global variability is large, with many places receiving nearly half their precipitation from this ecosystem service. The largest potential impacts for changes to this ecosystem service are land-use changes across temperate regions in North America and Russia. Likewise, in semi-arid regions reliant on rainfed agricultural production, land-use change that even modestly reduces evaporation and subsequent precipitation, could significantly affect human well-being. We also present a regional case study in the Mato Grosso region of Brazil, where we identify the specific moisture recycling ecosystem services associated with the vegetation in Mato Grosso. We find that Mato Grosso vegetation regulates some internal precipitation, with a diffuse region of benefit downwind, primarily to the south and east, including the La Plata River basin and the megacities of Sao Paulo and Rio de Janeiro. We synthesize our global and regional results into a generalized framework for describing moisture recycling as an ecosystem service. We conclude that future work ought to disentangle whether and how this vegetation-regulated moisture recycling interacts with other ecosystem services, so that trade-offs can be assessed in a comprehensive and sustainable manner.
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