Trumpeter Swans and Climate Change

Trumpeter Swans and Climate Change

Trumpeter Swan by John Van Orman

The effects of climate change on Trumpeter Swan populations will likely be complex and will differ across their extensive range, which spans much of North America. Scientists have documented a shift in range for various species due to warming temperatures. As is the case with Trumpeters, as ranges shift northward, there can be different problems to the south.

If one looks only at Alaska, there could be a positive aspect of warming temperatures for Trumpeters. Earlier, we pointed you to Dr. Joshua Schmidt’s 2009 Journal of Wildlife Management article in which he summarized the 5-year survey data showing Trumpeter Swans successfully breeding farther north in Alaska. He notes the possibility that northward range expansion in recent years may be due in part to climate change, citing a nearly 12-day increase in the number of ice-free days per year occurring over the last 100 years in Alaska. He suggests that it “is feasible that this increase in the number of ice-free days is enough to allow swans to breed in areas that were previously unavailable due to ice cover.”

A recent Blog, entitled World Climate Report  gleefully highlights this idea in their May 20th essay, and erroneously implies that the entire growth of the Alaskan Trumpeter population since 1968 is due to climate change. The Blog presents an idyllic photo of a Trumpeter with two cygnets, underscored with the caption “Trumpeter Swans Thriving in a World of Enriched CO2.” The authors appear to be unaware of the primary factors that fueled the increase of Alaskan Trumpeters, such as the cessation of the historic overharvest and the massive increase of agricultural food availability in their southerly wintering areas. It appears that the Blog is more focused on attempting to dismiss the serious problems caused by climate change than in increasing anyone’s understanding of the forces impacting Trumpeter Swan populations.

Authors of this Blog quote extensively from The Trumpeter Swan Society website  and chide TTSS for listing climate change as one of the problems facing Trumpeters. Unfortunately the World Climate Report made no effort to contact TTSS to understand why we include climate change as a problem facing Trumpeters.

Ruth Shea, TTSS Board Member and long-term advocate and biologist for the vulnerable Greater Yellowstone Trumpeter Swan population cautions us keep a 360° view. Commenting on the Blog, she replies:

“Since I wrote the information they quoted from our website- I thought I’d make a few comments. Basically, it is possible that Trumpeters in some areas may benefit from a warmer climate, since breeding range is often limited by the ice-free period and winter severity limits use of some potential wintering sites. However, in locations where the shallow wetlands essential for Trumpeter Swan nesting are drying up at an increasing rate, problems are developing. Here in the Intermountain West, warming climate is impacting the nesting habitat of an already fragile population and could prevent its recovery if this trend continues. We are seeing declining water levels in many historic nesting sites, and are losing crucial water supplies even on some key National Wildlife Refuges. Some important territories in Yellowstone National Park are now completely unusable due to declines in the water table. One of our greatest challenges will be to figure out how to maintain adequate breeding habitat for this population if this trend continues. If we fail, the future of this nesting population will be in jeopardy.”

If the hosts of the World Climate Report had come to us to inquire why we list climate change as one of the problems facing Trumpeter Swans, we would have explained our concerns. As we have for over 40 years, we’ll celebrate success in one area, while keeping a watch on all sides of the issue and presenting the most accurate information available. If the World Climate Report had not closed their comment period so quickly after posting their essay, we would have submitted our comments to them. As always, we welcome your comments here.

Find more John VanOrman photos at www.vanormanphotography.photoshelter.com

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One Response to “Trumpeter Swans and Climate Change”

  1. Josh Schmidt Says:

    The change in the breeding distribution of trumpeter swans in Alaska is a complicated issue. Trumpeters are recolonizing much of their historic breeding range, and this probably has little to do with climate change. On the other hand, they are now breeding in areas that were not likely part of their historical range, and this appears to be linked to a longer growing season. However, this short-term “benefit” of climate warming could be outweighed by larger-scale climate warming effects (e.g. wetland drying). The results of recent research suggest that shallow wetlands are drying across many areas of the state. Because swans use these wetland types extensively, this could dramatically reduce the amount of habitat available for breeding swans. The bottom line is that swans are extending their range, but densities within that range could decline sharply depending on the amount and extent of wetland loss. The expansion of the breeding range is only a part of the overall picture and it is very misleading to suggest that swans are benefitting from climate change without considering additional, larger-scale effects on the entire population. A small change in range extent is irrelevant if there are no wetlands left in which to breed. I would be interested to hear others’ thoughts on this issue.

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