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How can we adapt to climate change? One way to focus thinking on this challenge is to rephrase the question: How can we adapt to water change?

Because of all the various disruptions that scientists predict could occur due to a warming planet, changes in how water melts, falls and flows are among the most consequential for humanity — changes like:

  • Rising sea levels;
  • Stronger storm surges;
  • Melting glaciers;
  • Changes in rainfall patterns;
  • More rapid evaporation (from lakes, the soil and through plants); and
  • Increased frequency of both droughts and floods.

The implications of these changes include increases in deaths and damages due to floods (already the world’s most costly type of natural disaster), major disruptions to agriculture, and reductions in the amount and reliability of water supplies.

Hardly minor inconveniences, right? These are blows that could strike at the foundation of secure, functioning societies. And much of the harm would be inflicted on the world’s most vulnerable populations.

So how do we even begin to address these potential problems?

Global cooperation may yet work to avoid the most extreme of these forecasts. But even the current goal of holding warming to 2° C (3.6° F) would likely generate disruptions that would exacerbate the planet’s already existing great water challenges:

But as nothing focuses the mind like a hangman’s noose, these dire and interacting challenges can inspire novel ideas for escape.

One such idea is called “ecosystem-based adaptation,” or helping society respond and adjust to disruptions caused by climate change through the restoration or conservation of functioning ecosystems.  This concept can perhaps most easily be explained through an example.

In a paper and podcast in this week’s issue of Science, several colleagues and I focus on a particularly promising form of ecosystem-based adaptation: reconnecting or conserving floodplains (low-lying areas adjacent to rivers) so that they can provide their natural function of storing floodwaters.

The Yolo Bypass while flooded.  The Bypass is a 64,000 acre floodplain connected to the Sacramento River that reduces flood risk, provides habitat, recharges groundwater, and greatly increases the flexibility of California's water management system.

In much of the world, floodplains have been disconnected from rivers by flood-control infrastructure such as levees (barriers that are constructed alongside rivers that prevent floodwaters from spilling out onto floodplains) and dams (which capture and store floodwaters).

Relying solely on this “hard infrastructure” can court disaster — because success requires meeting a series of precise but often faulty assumptions:

  • That designers know the size of future floods (but a warmer climate will produce bigger floods);
  • That infrastructure will be well maintained (but levees have often been poorly maintained);
  • That the upstream watershed won’t change (but ongoing development replaces rainfall-absorbing wetlands and forests with streets and parking lots, which send rainfall rushing into rivers); and
  • That people will avoid dangerous areas (but a false sense of security leads people to put their houses in harm’s way).

Even without climate change, floodplain managers increasingly recognize that flood risks are rising and that we have become overly reliant on hard infrastructure and all its assumptions. Organizations such as the Association of State Floodplain Managers now call for augmenting hard infrastructure with the “green” or “natural” infrastructure of wetlands and floodplains.

Floodplains in their natural state have always soaked up and stored floodwaters, reducing flood levels downstream. By strategically removing levees or setting them back from the river, floodplains can be reconnected to rivers and once again perform this function. If done on a sufficiently large scale, floodplain reconnection can reduce flood risk for up- and downstream areas. The green infrastructure of floodplains can replicate or augment the functions of hard infrastructure such as dams and levees.

And the specter of climate change makes the natural infrastructure of floodplains even more valuable. Climate modelers forecast that a warmer Earth will have a higher frequency of both floods and droughts: longer dry periods will be punctuated by intense storms in which pounding rainfall runs quickly off the parched ground. This pattern will place enormous strain on water-management systems as managers try to balance the need to maintain reservoirs as full as possible to secure water supplies with the need to maintain partially empty reservoirs to capture floods when they do come.

Floodplains can help society adapt to these challenging conditions. For example, when floods move onto floodplains, much of the water percolates into the soil and recharges the groundwater (replicating the storage function of water supply reservoirs). And by shifting some of the storage of floodwaters onto floodplains, reservoirs can be maintained at higher levels, boosting water supplies and other benefits (such as hydropower).

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So by restoring one of the most important — and threatened — ecosystems in the world, we can reduce flood risks, increase the resiliency of water management systems, recharge groundwater, and promote biological productivity that supports fish, wildlife and people. All of these benefits can help society adapt to the potential disruptions from climate change.

In future posts, I’ll expand on this concept with specific examples. And I hope I can also talk about how the climate summit in Copenhagen has resulted in tangible support for ecosystem-based adaptation.

(Image 1, 2 & 3: The Yolo Bypass when flooded. The bypass is a 64,000 acre floodplain connected to the Sacramento River that reduces flood risk, provides habitat, recharges groundwater and greatly increases the flexibility of California’s water management system. Image 1 & Image 3 credit: Bruce (bioflyer)/Flickr through a Creative Commons license. Image 2: Yolo Bypass when flooded. Image credit: William Harrell/California Department of Water Resources.)

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