Created mitigation ponds fail to mimic the ecological functions of natural ponds

Temporary ponds (also called vernal pools, ephemeral or seasonal ponds, woodland pools) are abundant across the landscape. These ponds hold water for part of the year and provide critical habitat for a variety of species, such as amphibians and invertebrates, that cannot tolerate permanent water bodies (mainly due to predators such as fish).

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A natural temporary pond used as a reference site in the study (photo credit: Meredith Holgerson)

Unfortunately, these small temporary ponds are relatively easy to destroy. As such, ponds are often filled in for human development or agriculture. To minimize the loss of ponds on the landscape, new ponds can be created as mitigation. But a key question remains: do created ponds function as well as natural ones?

Mary Beth Kolozsvary (Siena College) and Meredith Holgerson (Yale University, visiting PhD student in the Strecker Lab) addressed this question in a study published last month in Wetlands. They compared seven seven-year-old created ponds to six reference ponds in New England. They found that created ponds were smaller in size, received more sunlight, had greater amounts of cattail and Phragmites, and were less likely to dry. The macroinvertebrate communities starkly differed, and created pools had fewer focal pool-breeding amphibians (spotted salamander and wood frog). Overall, they concluded that the ability of created pools to mimic the physical conditions and ecological functions of natural temporary pools was suspect.

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A created pond used in the study (photo credit: Louis Berger Consulting)

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2 responses to “Created mitigation ponds fail to mimic the ecological functions of natural ponds

  1. And why am I not surprised that the restoration/construction of temporary pools is not working on an ecological level? I would much enjoy the opportunity to meet with Ms. Holgerson to talk about vernal pools, having spent a good part of my later career looking at left coast vernal pools. You might be able to finally clarify for me the difference between an east coast vernal pool and a west coast vernal pool. I read E. Colburn’s book, all the while confused about why these eastern woodland ponds were called vernal pools.

    • Hi Stephen–
      I would love to chat with you about vernal pools! I agree the term “vernal pool” is an unfortunate misnomer for most of the ponds in the northeast as many of them actually fill with water in the fall or winter. There are many, many names for these ponds out there, which is too bad as I think it confuses people! Anyway, feel free to email me: maywood@pdx.edu.
      Cheers,
      Meredith

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