Investing in Natural Infrastructure: Restoring Watershed Resilience and Capacity in the Face of a Changing Climate

With changing climate conditions and intensified human use, the natural infrastructure provided by healthy, functioning watersheds—wetlands, soils, watercourses, aquifers, and floodplains—is currently under threat of loss at an unprecedented global scale. To meet the challenge, a step-change in investment and attention is needed by society to restore the natural capacity and resilience of watersheds so that present and future generations may enjoy the goods and services they provide. Losing the natural infrastructure associated with watersheds can weaken resilience to rapidly changing climate conditions and ultimately hinder economic development and human well being. Yet, natural infrastructure is widely overlooked when it comes to investment decisions; it is the built infrastructure—dams, reservoirs, and flood barriers—that tends to be given precedent by markets, investors, and policy makers. The challenge is to uncover, and bring to the foreground of awareness, the underlying value of natural infrastructure so that better decisions may be made and resources allocated.

Watersheds in a Changing Climate

Forming a dynamic zone of convergence between land and water, the major watersheds of the earth serve as unique geological, ecological, and biological domains of vital importance to a vast array of terrestrial and aquatic life. Given this abundance, it is perhaps not surprising that rivers and the watersheds that support them have long served as a focal point for human activity on planet Earth. Yet, rivers and watersheds around the world are currently undergoing significant and noticeable changes due to changing climate regimes. Observed climate variability and extreme weather events are now adversely impacting watershed systems worldwide, placing significant pressure on the natural infrastructure that provides the goods and services people need and desire (IPCC 2007).

For instance, in North America, the Intergovernmental Panel on Climate Change (IPCC) and the U.S. Climate Change Science Program (CCSP) recently concluded that climate change will directly affect watersheds and water resources in the Intermountain West in the observable future. While total annual precipitation appears to be increasing in the northern latitudes, and average precipitation over the continental U.S. has increased, the western and southwestern U.S. are trending toward reduced precipitation. In the context of higher temperatures, this reduction in precipitation will likely result in lower soil moisture and a substantial effect of runoff in rivers (IPCC 2007, USCCSP 2008a). Scientific consensus suggests with a high level of statistical confidence that more intense precipitation events are likely to increase in frequency, increasing flood risk in the region (IPCC 2012).

Vegetation cover, an integral part of the natural infrastructure associated with healthy watersheds, can be negatively affected by the stresses induced by climate change. Direct effects include die-off during drought and blow-down of trees during storm events. Indirect climate-sensitive disturbances include invasive species infestations and increased wildfire (USCCSP 2008). Studies also have concluded that changes to runoff and streamflow would have considerable regional scale consequences for economies as well as natural ecosystems (Milly et al. 2005). Such changes suggest the need for much greater levels of investment in natural infrastructure to restore adaptive capacity and enhance the resilience of watersheds to climate variability.

Investing in Natural Infrastructure

Thinking in terms of natural infrastructure and how it may be affected by changing climate conditions provides a useful basis for focusing investment in watershed restoration in the 21st century. Watershed investment does not replace the need for built infrastructure, but instead provides a critical complement, potentially multiplying the benefits received from healthy, functioning watersheds (Smith 2010). For example, dams can benefit from upstream forests that stabilize soils and hold back erosion. Wetlands that feed into reservoirs provide filtration services that improve water quality and reduce the need for purification. In short, the concept of natural infrastructure facilitates linking social investment in critical ecological processes within watersheds to the delivery of ecosystem goods and services that provide value to people over time. Ecosystem goods and services form a fundamental connective link between people and what they value in ecological systems (Daily 1997, DeGroot et al. 2002, Wilson...