A recent study
by two NPS scientists appearing in the journal PLOS One concludes that America’s national parks are already experiencing the impacts of climate change. The article begins by explaining that the management goal for national parks is a set of desired future conditions. According to the article, management of national parks has “for decades worked to preserve areas and resources within a ‘historical range of variability.’” In order to evaluate whether this management practice can continue in light of climate change, the authors evaluate the climate over the last 10 to 30 years in each national park compared to the conditions from 1901 to 2012.
To evaluate the difference between current and historical climates, the authors compared the average conditions over the last 10, 20, and 30 years to the historical average conditions in the 289 existing national parks. While finding that current temperature conditions are significantly different from historical averages in most parks, the authors conclude that there is not a linear trend in the changes when comparing the 10, 20, and 30 year periods.
Evaluating annual mean temperature in the parks, the study finds that 91% of parks exceed the 75th percentile in historic temperature distributions over the past 10, 20, and 30 year periods and that 55% of parks exceed the 95th percentile of historic temperature distributions. In contrast, when evaluating changes in precipitation, the study finds that most parks have recent precipitation profiles that are consistent with their historical average. In examining the ability to classify parks by temperature or precipitation regimes, the study concludes that “most parks are presently dominated by extreme high temperatures.”
Based on the study results and other available literature, the authors reach the following conclusions about national parks on a regional scale:
- Parks in the desert Southwest have become warmer and drier;
- Parks in Hawaii have become warmer and drier;
- Parks in the Northeast have become warmer and wetter;
- Parks in the Midwest are warmer; and
- Parks in the Southeast exhibit a “warming hole.”
Overall the study finds that many national parks are already experiencing temperature extremes with respect to historical averages. The authors further note that other studies have already documented measureable responses of plant and animal communities to climate changes. As climate regimes in the national parks continue to shift outside of their historical ranges, the authors suggest that additional analyses and potential new management regimes will be needed to assess the vulnerability of national parks and manage park resources under changing climate conditions.
It is important to note that national parks do not exist in isolation but rather have important interactions with the surrounding ecosystem. The findings of the NPS study are therefore not confined to the park boundaries themselves, but are likely also reflective of shifts in temperature and precipitation regimes in the areas surrounding the national parks. Understanding the climate impacts and management responses in national parks will therefore not only be important to preserving the parks as a valuable resource for all Americans but also because they may have implications for surrounding state and private lands.
Posted by Margaret E. Peloso
at 7/8/2014 4:53 PM