Restoration + climate change = cognitive dissonance
Submitted by Brandon Bestelmeyer on Tue, 04/08/2014 - 16:15
Last week, an agricultural researcher from the Monte Desert in Argentina emailed me to put him in contact with a seed supplier in the US. They wanted seeds of the perennial grasses blue grama and Lehmann lovegrass for some revegetation trials. I wanted to hit reply with: ¡Por favor, no lo hagas! (don’t do it).
Blue grama, a native grass in the western US (the state grass of New Mexico, in fact) I know and love, but it can be highly dominant where it occurs and it excludes other plant species. Lehmann lovegrass is an African grass that was planted in degraded rangelands to increase forage production, also used in roadside stabilization, that has become invasive in the southwestern US. Several papers indicate potential negative effects of Lehmann on biodiversity due to its aggressive spread and negative relationships between its abundance and those of certain native species. The Monte Desert has a wonderful assemblage of native herbaceous species, so why would you introduce either of these exotic plants into that ecosystem, given what is possible (blue grama) and what we have already seen happen (Lehmann)?
Last week I also read the latest IPCC report on climate change effects. One passage hit home: “The paleoecological record and models provide high confidence that it will be difficult or impossible to maintain many ecological systems in their current states if global warming exceeds 2 to 3°C, raising questions about the long-term viability of some current protected areas and conservation schemes, particularly where the objective is to maintain present-day species mixtures”. The report also states that there is “limited evidence and low confidence” that warm, arid grasslands and shrublands, like the Monte, will experience a loss of biomass production (that is, less of everything).
I came to experience what psychologists refer to as cognitive dissonance: the discomfort in holding two contradictory beliefs at the same time. On the one hand I am concerned about a potentially invasive species disrupting a plant community, on the other hand I know it’s going to be disrupted anyway and that it probably doesn’t matter. Or maybe having a few more perennial grasses in the game could increase “climate resilience” and the likelihood that any perennial grass will persist in the Monte through the coming decades. An argument can be made that Lehmann lovegrass provides this function even now to parts of Arizona that experienced grass loss and soil degradation long ago.
Restoration efforts in southwestern New Mexico create a parallel source of discomfort. The removal of woody plants by federal agencies, using chemical or mechanical means, is explicitly directed at restoring degraded areas to a grassland structure that existed before 1900. In many cases we are getting some perennial grasses back. But what if desert shrublands are the best we can hope for in the hot, dry years of the 2080s? What if the limited grassland recovery we have seen to date is reversed by prolonged droughts and the woody plants do not recover either? In restoring elements of the past to the present, do we cause desertification in the future?
We are not prepared psychologically, intellectually, or institutionally to respond to such questions. The community of land users, managers, and policymakers still believes that the historical range of variation is our goal for the future—that belief is codified in government policy. There has been a great deal of writing to shake this foundation, most notably papers by Richard Hobbs and colleagues suggesting that we should consider more open-ended goals in management, including the value of “novel ecosystems” that have no historical precedent. But these ideas are hard to put into practice because of the great uncertainty involved in creating alternative goals (such as by letting invasive species persist) and our ignorance of what climate resilience actually entails (resilience of what exactly, and, assuming we know what that is, to what degree of change in climate?). As Nicole Heller and Hobbs wrote in a recent paper, “Management rhetoric seems paradoxically to ask that managers allow for change so that ecosystems can adapt but also that they not permit change so that systems can remain intact (i.e., not damaged or impaired).” This paradox, plus the uncertainty, leads to inertia. We continue to manage for what we can measure and understand.
I will go out on a limb to suggest alternative, measurable, resilience-based goals for the Monte and Chihuahuan Deserts. Maintain the ecosystem’s ability to produce biomass and stabilize soils in the face of weather variability. Conserve, to the extent possible, species diversity and endemic species of the region. Identify options for maintaining human livelihoods, including adaptation (such as a shift in livestock breeds) and transformation (such as a shift to mesquite bean farming and honey production). The devil is in the details of how much of what happens where, but nothing here is very new or unreasonable. Confronting those goals with data-driven, logical, and imaginative appraisals of invasive species and woody plants, on the other hand, might lead to radically new management practices, greater comfort with some controversial ones, and less comfort with others.