Revealing Invisible Water: Moisture Recycling as an Ecosystem Service

Abstract

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.

Resilience (Republished)

“…Interconnections of humans in a globalized society can propagate and cascade across countries and regions (e.g., Adger et al 2009, Liu et al 2013, Eriksson et al 2015, shaping landscapes, seascapes, the well-being of people and social-ecological systems worldwide (e.g., Holling 1995, Hughes et al 2003, Fairhead et al 2012, Galaz 2014, Lazarus 2014. Keys et al 2016.…”

On the social dynamics of moisture recycling

“…We emphasize that the WAM-2layers is a moisture tracking scheme and not a simulation. It is possible to couple the WAM-2layers with dynamic simulations of land-surface hydrology, including vegetation Keys et al, 2016), but that is not what we have done in this research. Thus, the results that we present are based purely on the implicit hydrological information contained within the ERA-Interim Reanalysis data.…”

“…To find regions that are both relevant to terrestrial moisturerecycling dynamics, as well as (potentially) relevant to social dynamics, we use regions selected from the work in Keys et al (2016), who identified global regions that are particularly reliant on current vegetation for rainfall from moisture recycling see Fig. 2b in the present paper).…”

“…Many approaches for precipitationshed boundary selection have been described (Keys et al, 2012(Keys et al, , 2014(Keys et al, , 2017, and we will employ the 1 mm boundary as used in Keys et al (2014). The basis for the 1 mm boundary in this instance is to have a boundary that is physically meaningful, at least theoretically, in the sense that common rain gauges have a lower limit of 1 mm.…”

“…The range of social topics that have been explored in the context of moisture recycling include natural hazards and flooding (Dirmeyer and Brubaker, 1999;Dominguez et al, 2006), irrigation impacts on moisture recycling (Lo and Famiglietti, 2013;Tuinenburg et al, 2014), rainfed crop production (Bagley et al, 2012;Keys et al, 2012), ecosystem services (Ellison et al, 2012;Keys et al, 2016), urban water vulnerability , and even the import and export of moisture among nations (Dirmeyer et al, 2009;Keys et al, 2017). Land-use change impacts on rainfall via moisture recycling have been suggested to be potentially linked to the Sahel drought during the 1970s, and this moisture-recycling mechanism was suggested to be an integral part of the socio-hydrology discipline (Sivapalan et al, 2012).…”