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Abstract

In a world where the metrics of the carbon economy have become a major issue, it may come as a surprise that intact cold desert shrublands can sequester significant amounts of carbon, both as biomass and in the form of SOC (soil organic carbon). Xerophytic shrubs invest heavily in belowground biomass, placing fixed carbon in an environment where it turns over only very slowly. In order for humans to gain this important ecosystem service, desert shrublands must be kept intact and prevented from frequent burning. The biggest threat to shrubland integrity is the invasion of exotic annual grasses that increase fire frequency to the point that most shrubs can no longer persist. Not only do annual grasslands sequester very little carbon, they also increase the turnover rate of existing SOC. From the point of view of carbon sequestration, restoring the many millions of hectares of annual grass dysclimax in the Interior West to functioning shrubland ecosystems should have high priority. The elimination of perennial understory vegetation and cryptobiotic crusts is a nearly inevitable consequence of livestock grazing in deserts. This opens these systems to annual grass invasion, subsequent burning, and loss of a major carbon sink, a heavy price to pay for the minimal economic gains derived from direct use of these intrinsically unproductive lands for livestock production. On a more immediate scale, the conversion of stable desert shrublands to annual grasslands that burn frequently has also created major issues with windblown dust. Good evidence exists to show that deposition of this dust on mountain snowpack can have the effect of reducing water yield by causing premature melting. Water is clearly the most limiting resource for agriculture in our region, and protecting mountain watersheds from dust deposition should become another important priority. As climate disruption in all its forms becomes a major threat to production agriculture, it is imperative that serious steps be taken to minimize this threat, including restoration of degraded shrubland ecosystems, and prevention of degradation of shrublands that are still intact. Here the argument is made that the best use of cold desert shrublands is mitigation of both short term and long term climate disruption.

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