While invasive plants and energy development threaten southwest rangeland, agricultural conversion remains at the top of the list of future threats. However, studies show that US rangelands are generally in good ecological condition and hasn't changed much over the past ten years.
Apr. 11, 2013
With drought-stressed hay conditions and a shortage of available forage on rangelands across the Southwest, the last thing we want to hear is that rangelands across America are at risk from invasive plants, continued energy development and other threats.
But a new report from the U.S. Forest Service warns of an expansion of invasive plants that threaten rangeland ecology and suggests other risks are possible that over time could cause widespread damage and change that could carry a hefty price tag with it in the years ahead.
On the brighter side, the report,“A Synoptic Review of U.S. Rangelands: A Technical Document Supporting the Forest Service 2010 RPA Assessment,” says U.S. rangelands are currently in relatively good ecological condition, with more than 75 percent of the land area exhibiting healthy characteristics.
That assessment, say Forest Service officials, is not much different than the 1989, 2000, and 2010 Range Assessment reports that indicated the total U.S. forage supply was sufficient to meet projected demands in the immediate future. But developing problems, including invasive plants, energy exploration and development, and climate change will require more explicit data describing the status and developing trends of the risks rangelands will facing in the coming years.
The ongoing risks of invasive plants
The Forrest Service estimates approximately 3,310 non-native plant species occur within the conterminous U.S. on roughly 50 percent of non-federal rangelands. The 16 most pervasive species affect 126 million acres and are expanding at a rate of up to 4000 acres per day, or approximately 1.5 million acres per year in some regions. Researchers say these rates are alarming and the area affected occupies about 1 million square miles, an area larger than Texas, California, Montana, New Mexico, Arizona, and Nevada, combined.
The research team, led by Matthew Reeves, research ecologist, and John Mitchell, emeritus scientist at the Rocky Mountain Research Station, warn that urban development, oil and gas exploration, agricultural development, and to a lesser extent, residential development could all further add to rangeland fragmentation.
Researchers say rangelands are a source of both renewable and non-renewable energy in the United States. Of all energy sources extracted from rangelands, coal, oil, and natural gas are by far the most common. However, the large, windswept, arid rangeland landscapes of the western U.S. are uniquely poised to provide substantial quantities of wind and solar energy and limited rangeland areas are subject to new fracking methods designed to remove shale oil deposits that could generate pressure on rangeland ecology.
“Globally, rangelands occupy nearly one-half of the vegetated surfaces and at least half of these lands are grazed and provide livelihood to millions of people,” the report reads.
It also warns global pasturelands have shrunk by approximately 4.7 million acres per year since 1995, largely at the expense of expansion in agricultural land use. Changes in rangeland extent in the future are difficult to predict, but projected increases in global population will undoubtedly result in further conversion of pasture and rangelands to agricultural uses. At the same time, sharp increases in demand for red meat will require greater output of goods and services per area of land.
Multiple resources at risk
Rangelands in the United States provide extractable goods, such as plant materials, as well as tangible and intangible rangeland ecosystem services, such as clean water, carbon sequestration, and renewable energy. But of greatest importance is forage and feed supply in support of livestock and wildlife.
The report indicates the total forage supply is near 1.9 to 2.6 trillion pounds. Based on this estimate, the forage situation is positive and forage quantity is sufficient to support roughage requirements of wild and domestic herbivores now and into the foreseeable future. But forage supplies could decline as threats begin to affect rangeland ecology at the expense of other resources.
In addition, concepts of rangeland health are still evolving. The extent and remoteness of rangelands make assessing health and vitality difficult. No national monitoring framework is in place to collect data over time and, unlike the Bureau of Land Management (BLM) and Natural Resources Conservation Service (NRCS), the U.S. Forrest Service currently has no data collection protocol permitting evaluation of rangeland health on all lands under their control.
Invasive plant species have continued to increase in spread and density, and estimates of expansion over time are reflected by the growth in concern over the associated problems. The size and scope of the problem, and the generally uncoordinated approach toward controlling invasive species, make determining the amount of effort committed to combating invasive species difficult. Despite this difficulty, in the year 2000, the total annual cost was estimated at $137 billion in losses and direct expenditures. Those numbers will grow rapidly in the years ahead.
Despite the scope of the problem, the invasive species situation is not hopeless and substantial investments in control and mitigation efforts have been made.
USFS says U.S. rangelands are not in imminent danger from the many risks and threats that exist today. But they advise more awareness and monitoring will be required in the years ahead if rangeland ecology and productivity is to be preserved for future generations.
In spite of the many risks, present and future, the most pressing may well remain severe drought conditions that continue to stress not only the Great Southwest, but also growing regions across America’s midsection.