Friday, June 26, 2015

Climate Trajectories for Colorado's Terrestrial Ecosystems

By Karin Decker, CNHP Ecologist

Recently we blogged about CNHP’s Conservation Planning Team evaluating the potential effects of future climate conditions on Colorado’s species and ecosystems. An important part of this work is to look at projected future conditions in comparison with recent climate patterns. The graph below shows the projected direction of change in the current location of Colorado’s major terrestrial ecosystems as described by average annual temperature and precipitation.

Projected seasonal average precipitation and mean temperature trajectories for current upland ecosystem ranges in Colorado summer by mid-century under a high radiative forcing scenario (RCP8.5).
A comparison of recent average values of climate variables with projected values for the current locations of these ecosystems in Colorado show shows seasonal differences both in the direction and amount of projected changes in temperature and precipitation. For instance, ecosystems of higher elevations (e.g., alpine tundra and spruce-fir forest) are projected to experience a greater increase in winter precipitation than those of lower elevations (e.g. sandsage and shortgrass prairie), although the amount of warming is similar for all elevations. Projected changes in summer precipitation are generally less than for winter, with some ecosystems seeing a slight increase and others a slight decrease.

Of course average temperature and precipitation patterns are not the whole story. The interaction of climatic conditions with other abiotic factors (e.g. soils, disturbance), life-history traits of the component species (e.g. growth form, dispersal mechanisms), and past history shapes the observed distribution of ecosystems. Because many of the characteristic species of these ecosystems are long-lived, the time lag between the onset of new climate conditions and the response of the species to those conditions, adds another level of uncertainty to projections of future distribution. Climate changes over the past few decades are probably already facilitating a gradual modification of ecosystem extent and species composition that will become more apparent by mid-century.

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