A new study from the U.S. Fish and Wildlife Service points to agricultural conversion as the chief reason wetlands and grasslands have been lost in the prairie pothole region, while also noting farmers’ conservation efforts account for most wetland recovery recorded during the study period.
According to “Status and Trends of Prairie Wetlands in the United States 1997 to 2009” released this week, the USFWS said agriculture accounted for 95% of wetland area lost during the period.
The study stopped short of pointing to ethanol and other biofuels as a driver in the loss of wetlands and grasslands in the prairie pothole region of North Dakota, South Dakota, Iowa and Minnesota. Recent land conversion reports by environmental groups have specifically laid the loss of wetland habitats on the run-up in corn prices driven by need to feed ethanol plants.
The 80-page USFWS study makes only a passing reference to biofuels and breaks no new ground on the question of how much — if any — blame should be laid on expanded ethanol production.
“A number of studies have shown that agricultural drainage continues to be one of the greatest threats to wetlands in the PPR,” the study said. “The continuing emphasis on increased crop production for biofuels places additional pressure on wetland conversion to agriculture in the PPR.”
A study earlier this year by the Environmental Working group came out more strongly against biofuel production in regard to wetland conversion. That study was based on satellite imagery from a more recent period, 2008 through 2012.
The USFWS study said farmed wetlands declined by an estimated 45,310 acres between 1997 and 2009. An estimated 6,175 acres, or 13.6%, of these areas were converted to other wetland types. Some 86% of farmed wetlands were converted to upland agriculture.
“The loss of farmed wetland to upland agriculture was determined by the loss by wetland hydrology (i.e. drainage via ditching, tile drains or land leveling fill in some cases),” the study said. “These farmed wetlands are very vulnerable to drainage because they are usually small, in close proximity to existing farm field operations and can be easily drained, usually without penalty under existing regulations.”
Wetland losses to agriculture between 1997 and 2009 came from the conversion of farmed wetlands and small temporarily flooded emergent wetland basins, according to the study. Farmed wetlands are wetlands tilled for agriculture that retain their wetland characteristics.
Between 1997 and 2009, an estimated 87,690 acres of emergent wetland was restored from agricultural lands, according to the study. “These restored wetlands averaged 5.8 acres and were seasonally or semi-permanently flooded areas,” the study said.
“The results of these wetland restoration efforts were overshadowed by the loss of 125,400 acres of emergent wetland converted to upland agriculture. The deficit, represented by a loss of 37,770 acres, indicated that the no-net-loss of wetland policy goal had not yet been reached in this region.”
Previous DTN reporting found that farmers in South Dakota, for example, have turned to tiling to drain farmed wetlands that in some seasons would not otherwise be available for production.
While tiling has been helpful to production agriculture in the region, the study said the practice contributes to wetlands loss and jeopardizes recovery efforts.
“Subsurface tile drainage systems have been popular with some landowners for removing surface waters and wetlands in both southwestern Minnesota and Iowa, and this trend has extended into portions of the Dakotas,” the study said. “In some areas, these drainage networks are so extensive they have effectively altered regional hydrology and may have ramifications for the success of any future wetland restoration projects that attempt to reestablish hydrologic connectivity to wetland complexes.”
The study said temporary wetlands are a “major component” of the wetland ecosystem, accounting for an estimated 49% of all remaining wetland basins in 2009. The study said losses of temporary and farmed wetland area approached 133,000 acres between 1997 and 2009.
Despite agriculture’s role in lost wetlands, the study said “the majority of emergent wetland restoration or creation in the PPR stems from conservation programs on agricultural lands or agricultural land management approaches.
“Conservation provisions as part of the farm bill legislation have deterred some wetland drainage for crop production in the Dakotas, but have not totally eliminated wetland losses to agriculture,” according to the study. “Studies indicate that considerable wetland gains (upwards of 59% of wetland restoration or creation) by area occurred on agricultural lands between 1997 and 2007.”
The study found that grassland accounted for about 21.1 million acres in the prairie pothole region in 2009. Total net losses of grasslands in the region between 1997 and 2009 totaled about 568,000 acres.
The USFWS said while the “interaction between grassland and row-crop agriculture” was the primary cause for land use change in the region, non-agricultural land use accounted for some 27,310 grassland acres lost. That includes expanding urban areas and infrastructure. Loss of grassland habitat has also been reported owing to planting trees and suppression of grazing and fire in the prairie region, the study said.
“The annual rate of loss of grassland area was estimated at 0.2%,” the study said. “An estimated 95% of the grassland area lost between 1997 and 2009 was attributed to agricultural operations, primarily crop production. There is inherently some overlap between grassland as defined in this study with agricultural lands. For example, agricultural fields planted to alfalfa as a crop rotation practice or fallow fields are still agricultural lands that produce ‘grass.’
“It is likely that grassland to cropland conversion will increase if agricultural commodity prices continue to follow recent trends.”