Association of State Wetland Managers - Protecting the Nation's Wetlands.

New Reports Show Alarming Trend of Wetland Losses in the World

Guest Blog by William J. Mitsch Ph.D

In a report just issued for discussion at a global wetland meeting scheduled for early June in Uruguay, Gardner et al. (2015) gave an astonishing fact that global wetlands are estimated to have declined by 64 to 71 % in the 20th century alone and that this degradation rate continues.  As pointed out in our most recent edition of the book “Wetlands, 5th ed.” (Mitsch and Gosselink, 2015):  “The rate at which wetlands are being lost on a global scale is only now becoming clear, in part with the use of new technologies associated with satellite imagery. But there are still many vast areas of wetlands where accurate records have not been kept, and many wetlands in the world were drained centuries ago…It is probably safe to assume that (1) we are still losing wetlands at a fairly rapid rate globally, particularly in developing countries; and (2) we have lost half or more of the world’s original wetlands.”

In a paper cited in the above report and book, Davidson (2014) determined that the world lost 53.5 percent of its wetlands “long-term” (i.e. multi-century) with higher loss rates in inland vs. coastal wetlands (60.8 vs. 46.4 percent respectively). He also found out that the wetland rate of loss in the 20th –early 21st centuries was 3.7 times faster than the long-term loss rate.

wetlandsmitschIn the USA, we have sound estimates that we lost about half of the wetlands in the lower 48 states equivalent from the 1780s to the 1980s.  That translated to an enormous loss rate of 236,000 hectares (580,000 acres) per year of wetlands for almost 2 centuries!  Even from the 1970s to the mid 1980s, we were losing over 100,000 hectares (260,000 acres) per year.  In stepped the Federal courts’ interpretation of the Clean Water Act to include wetlands as “waters of the United States” and the loss rate plummeted to about 5,600 hectares (14,000 acres) per year in the latest assessment issued a few years ago.  We have not yet achieved the national goal of “no net loss” that has been the formal policy of the USA for 30 years, but we are getting close and are much better off than most of the rest of the world in conserving the wetlands that are left.

But the legal means that we use in the USA to protect wetlands will not work in the rest of the world where land is needed for food production and living space for a growing world population. That makes slowing the global loss of wetlands that much more problematic. Rather we have to educate the world on the values of wetland ecosystems for the services that they provide for us including cleaning our water, supporting our biodiversity, mitigating our floods and coastal storms, and sequestering more carbon per unit area than any other ecosystems on the planet. In almost every comparison that has been done, the economic value of natural wetlands is at the top of the list.

I will be going to that meeting in Uruguay and will probe the validity of these world wetland trend estimates, but if the facts are even close to the ones I cite above, we need to sound an international alarm that “enough is enough.”  Please join me by forwarding this message around to any social or professional groups that you link with so that the alarm can be heard world-wide.


Davidson, N.C. 2014

Gardner, R.C. et al. 2015

Mitsch and Gosselink, 2015, Wetlands, 5th ed

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