Shrinking Ponds

Approximately 12,000 lakes and ponds now dot the landscape of Denali. Although water level controls in these ponds are complex, recent research suggests that some ponds may be subject to increased evaporation due to climate warming and accelerated drying due to thawing of permafrost that would otherwise inhibit drainage.

Repeat photo pair comparisons showed some ponds to have dried significantly, while others showed very little change. As we try to determine whether a change identified in a photo pair is indicative of succession or a larger-scale change related to climate warming, it is also important to consider how ecological attributes captured by the photo pair may change cyclically. For example, a small pond may shrink during a warm, dry year and expand again during a wet summer. Therefore, it may be necessary to acquire several sets of photos over multiple years to be sure the interpretation of change is valid.

In general, scientists should practice caution when interpreting any single piece of evidence as definitive proof. Although a picture may “be worth a thousand words,” one must read the “words” carefully to avoid misinterpretation. As you browse the photo pairs, consider which features visible in the photo pairs might be evidence of a permanent change, and which might indicate a temporary or cyclical change?


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