Tuesday, January 23, 2007

NRCS Assessment of US Land Use, Erosion, Wetlands

The USDA Natural Resources Conservation Service has posted results of their Natural Resources Inventory (NRI). Depicted are land cover and use, soil erosion, and wetland gains or losses for the 48 contiguous United States.

From 1977 to 1997, NRCS conducted the assessment every five years, in 2000, they began the transition to an annual assessment. The most recent data is from 2003 and reflects only conditions at that point, NRCS Chief, Arlen Lancaster says, "This is a snapshot, this is the number in terms of cropland, this is where we're at in terms of erosion," he says later this year they will be able to provide numbers that reflect the change from year-to-year.

Some findings:

  1. The 48 contiguous states cover 1.9 billion acres and 71% of that, 1.4 billion is in non-Federal rural land uses. Of that 1.4 billion acres, 406 million is in forest land, 405 million is rangeland and 368 million is cropland.
  2. Cropland acreage decreased 12% from 1982 to 2003. The net decline between 1997 and 2003 was 8 million acres, or about 2 percent.
  3. Soil erosion on U.S. cropland decreased 43% from 1982 to 2003.
  4. In 1982, 40% of all cropland was eroding above soil loss tolerance rates, that number declined to 28% in 2003.
  5. Erosion rates on a per acre basis declined significantly between 1982 and 2003. Sheet and rill erosion on cropland dropped from 4.0 tons per acre per year in 1982 to 2.6 tons per acre per year in 2003; wind erosion rates dropped from 3.3 to 2.1 tons per acre per year.
  6. There was a net gain in wetland acres on non-Federal rural lands between 1997 and 2003. Annual net gains between 2001 and 2003 were 72,000 acres per year, of which 44,000 acres per year were on agricultural lands.

The 2003 results look fairly encouraging. Erosion continued down. There was a net gain in wetland acres coming substantially from agricultural lands and a moderated trend of farmland loss. It fits with what I was seeing on the ground in those years. 2004, 2005 and 2006 might not be as good as 2001 - 2003. Funding for soil conservation and especially wetland construction was tighter after 2003. This was also at a time when tiling was on the increase, as I reported earlier. The farmland loss rate probably regained some steam with development activity. Any comments?


mygaia said...

I have just found your blog. I am not a soil scientist but studied soil erosion in South Africa. Thought you might be interested in my blog which I'm trying to come to grips with. Soil Erosion in New Zealand

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