Sandra Postel, named by Scientific American as one of 50 Scientific Americans, director of the Global Water Policy Project, and author of a number of books, including Pillar of Sand, has dire warnings about the world water supply.
Conversion of land to agriculture and urban-industrial developments, new dam construction, building dikes and levees, large scale river diversion, groundwater withdrawals, and uncontrolled land, air and water pollution is continuing to damage an already fragile fresh water ecosystem, according to Sandra Postel, the keynote speaker at the 12th Annual Xeriscape Conference in Albuquerque, New Mexico.
Speaking to over 300 professionals (scientists, ecologists, horticulturalists, writers and other professionals) Postel gave a frank appraisal of what is happening globally to the world’s water supply.
Postel’s credentials are impeccable. An author of over 100 articles in both popular and scientific publications, she has also appeared on numerous television news programs and is an advisor to the U.S. National Research Council.
Here are some of her observations:
Conversion of land to agriculture and urban-industrial developments
- Alters the way rainfall is naturally divided between surface runoff and groundwater recharge.
- Affects quantity, quality and timing of water flows
- Causes sedementation in reservoirs
- Causes habitat reduction and species loss.
Dan Construction
- Fragments rivers and alters natural flow patterns.
- Changes water temperature, and the transport of nutrients and sediment. (Reservoirs have trapped more than 100 billion tons of sediment that would have been delivered to coastal regions).
Dike and Levee Construction
- Disconnects rivers from floodplains, eliminates habitats for fish and other aquatic organisms, and reduces the recharging of aquifers.
- Encourages human settlment in flood plains, increasing flood danger.
Large-Scale River Diversions
- Depletes flows to damaging levels.
- Causes habitat degratation on rivers, harms fisheries and causes loss of species.
- Reduces water quality.
- Degrades coastal ecosystems and lakes into which rivers empty.
Groundwater withdrawal
- Causes water tables to drop.
- Can reduce or eliminate springs and river base flows.
- Can deplete underground aquifers.
Uncontrolled land, air and water pollution
- Diminishes water quality.
- Causes habitat and species loss .
- Alters chemistry of rivers and lakes, destroying habitat, harming fish and wildlife and increasing risk to humans.
Introduction of exotic species
- Affects food webs, recycling of nutrients and water quality.
- f the world’s 10,000 freshwater fish species have become endangered, are on extinction watch, or have already become extinct.
- Contributes to species loss. At least 20% of the world's 10,000 species of reshwater fish species have either become endangered, are threatened or have already become extinct.
Already, effects of desertification are reaching throughout the world. In many non-urban areas, grass is drying up and oxidizing. Good examples of this in North America are areas in the deserts adjacent to the Great Plains. These areas were once grazed by migrating herds of bison. Once fenced off and overgrazed by livestock, remaining grasses began drying up and oxidizing, turning to desert.
Postel offers solutions to all these problems, but the solutions themselves don't come without consequence.
