By John Matthews, Conservation International
An enormous amount of attention has been paid to the loss of the ancient glaciers in the Himalayas and across the Tibetan plateau. Their retreat and the loss of glacial mass have been tied to rising air temperatures, longer warm seasons, and shifting precipitation patterns. But while dramatic and newsworthy, the loss of glaciers does not have an immediate impact on most people and ecosystems in the region beyond dry-season flows. Glaciers represent old reservoirs of water that build up over decades, centuries, and even millennia. However, most of the liquid water resources in the Himalayas and plateau come from seasonally frozen rain, groundwater, and snow, which accumulate each winter and melt over the following spring and summer to enter the rivers, groundwater, and lakes of south and central Asia.
I’ve just returned from two weeks on the Tibetan plateau, mostly in Qinghai province of western China, with a team from the China Program Office of WWF, WWF-US, and a colleague from the Qinghai State Forestry Administration. We were scoping climate change impacts and considering adaptation strategies for the region, with a focus on water resources.
The Tibetan plateau is especially sensitive to shifts in the timing of precipitation and the onset of spring, as well as the volume of frozen rain and snow that builds up over each winter. The area of the plateau is huge — about four times the size of France, occupying most of western China at an average elevation of 4500 m (16,000 feet). The majority of the people who live on the plateau practice an ancient livelihood of pastoral nomadism, centered on moving their herds of yak, sheep, and horses from low altitude (winter) pastures to high altitude (summer) pastures each year, a pattern called transhumance.
Within the past 15 years, however, this cycle has become starkly disrupted. In some counties, as many as three out of every five years are now called “snow disasters,” meaning no accumulation of frozen water before the onset of spring. Water in streams and rivers and in the soil does not freeze during these years but continues to flow downstream and away from upland slopes. Fallen snow melts or sublimates quickly instead of lasting until spring and summer. As a result, when the young grasses desperately need water most during spring, soils are dry and barren. The grasses wither or never sprout. The former misting light rains of summer now thunder down in pounding showers. And the soils, unlocked from their grasses, slump suddenly and begin to erode. The grasslands of the plateau — its “green glaciers” — are melting away.
Understandably, the people living on the plateau are extremely concerned about seeing pastures that were fertile and productive, full of high grass in recent decades, degrade to low lawns or dissolve to bare rock and soil. Fences have begun to snake their way across the landscape like long strips of fear, dividing the remaining grasslands and communities. These fences are attempts to reserve what’s left for individual families or regional residents. In some cases, however, these fences actually intensify grazing pressures, quickening erosion with additional trampling and browsing grasses down to their roots.
In effect, we are losing the grasslands of the Tibetan plateau as the vegetation and soil dissolve into the great rivers of the region — the Yangtze, the Mekong, and the Yellow. The loss of these green glaciers does indeed matter to both people and ecosystems. In some areas, government officials report that more than 2 percent of local grasslands are lost annually. Underfed yak herds are starving or are vulnerable to disease. The community of wild species is responding in strange ways across the region, too, with populations of grass-eating pikas and caterpillars exploding in some areas. Marmots enter hibernation much later in fall and emerge much earlier in spring. Even predators such as snow leopards and bear feel the pressure of reduced prey species such as blue sheep, and thus turn more often to domesticated species or invade the winter quarters of the herders. Older residents of the plateau say these changes are unprecedented over lifetimes spanning six or seven decades. And the impacts are rapid and recent.
Adaptation choices for the plateau are both difficult and limited in the face of such extremely rapid environmental change. Clearly, local livelihoods need to be diversified to reduce human-wildlife conflicts as well as grazing pressure on grasslands. Erosion control mechanisms will be viable in some regions, while other areas should be left fallow to recover slowly. And management strategies for agriculture and endangered species need to shift to reflect the changing characteristics of the landscape.
The Tibetan plateau of 20 years ago is already gone and a new plateau is emerging before us. The green glaciers — the Tibetan plateau’s grasslands — and the livelihoods and species that depend on them can adjust, but this process will require time and careful thought.