Riparian Restoration: More important than ever with climate change

For people in the conservation/restoration community, trying to deal with climate change is a tough assignment.  Years and years of training and conventional wisdom preaches the value of restoring habitat to a 'pristine' state.  In the U.S., that usually translates into Pre-European settlement.  However, the reality is that the pre-settlement environment may simply no longer exist.  Even if those conditions do exist, there's no guarantee that it is even possible for those ecosystems to be recreated (some species may now be extinct or extirpated, or those genotypes may be extirpated, or the particular sequence of events that allowed those ecosystems to persist may never again occur).

Getting past the goal of pristine restoration is not easy, in part because what goals are you going to use instead of pristine?  Obvious (to many research ecologists) is the use of various ecosystem services or functions as replacement goals.  Equally obvious is the conservation of particular endangered species.  However, doing this without realizing the rapidity with which environmental conditions are changing is likely to result in poor results.

Seavy et al. (2009; full cite below) recently published a paper in Eco Restoration that discusses some of these issues in relationship to the restoration of riparian areas.  They further argue that restoring riparian areas will provide benefits beyond the boundaries of the areas being restored.  Specifically, they argue that restoring riparian areas will improve overall ecosystem resilience in the face of changing climate.  Resilience (as defined by the authors) refers to the ability of an ecosystem to withstand disturbance without changing 'state', recover after disturbance, and the way an ecosystem responds to gradual changes.  Resilience is a tricky concept (over a large enough time scale, every ecosystem is in constant flux), but for timescales relevant to wildlife management, this is probably a useful idea.

Essentially, Seavy et al. (2009) argue that restoring riparian areas is likely to improve the ecosystem resilience of surrounding areas because 1) riparian areas are naturally very resilient, 2) riparian areas improve connectivity between ecosystems (aquatic and terrestrial; along longitudinal migration corridors), 3) riparian areas are natural thermal refugia, and 4) there are lots of flood-related benefits to "natural" riparian areas. So lots of benefits, but achieving those benefits (in spite of major climate change) will require some fancy work.  For instance, restoration plantings typically use seeds from species on-site or nearby.  However, if environmental conditions are likely to change, then those species (or those genotypes) may not be successful, and noxious or non-native species would have the opportunity to invade.

Ok, so that all sounds really good.  Some issues:

1)  There's a real emphasis in this paper on riparian woodlands, but there are some places where woodlands are rare, or absent entirely.  Should we plant woodlands along areas that haven't had them historically?  I don't know, but I don't know if we should, or if we should even encourage it.

2)  The authors talk about riparian areas being naturally resilient, but this is only really documented for persistence in the face of hydrologic variability (flood and, to a lesser extent, drought).  I'm not aware of any literature documenting any particular resilience of riparian ecosystems to disturbances related to temperature, invasive species, pollution or eutrophication.

3)  The primary benefit, that I can see, to prioritizing riparian restoration above other areas, is the reality that you are benefiting both terrestrial and aquatic habitats at the same time.  However, I think this ignores the integrated nature of watersheds.  I suspect that if you improve the non-riparian terrestrial components of a watershed, you're going to have similarly dramatic (if potentially different) positive effects on streams.  I guess I'm not convinced that it is a good idea to make riparian restoration a priority without consideration of what else is going on in the watershed.

Having said that, the paper does make a compelling case that riparian areas are really important, and that we need to adjust how we restore them, and that some important questions need to be answered if we are going to be effective at restoring these ecosystems in the future.

Summary:

Restoration of riparian areas will likely provide a lot of benefits in light of the rapidly changing global climate, even beyond the strict borders of these areas.  However, different techniques need to be employed to realize these benefits.

Seavy, N., Gardali, T., Golet, G., Griggs, F., Howell, C., Kelsey, R., Small, S., Viers, J., & Weigand, J. (2009). Why Climate Change Makes Riparian Restoration More Important than Ever: Recommendations for Practice and Research Ecological Restoration, 27 (3), 330-338 DOI: 10.3368/er.27.3.330