The award, which includes a $200,000 cash prize and gold medals, will go to David W. Schindler, holder of the Killam Memorial Chair and professor of ecology at the University of Alberta, and to professor Igor A. Shiklomanov, director of the State Hydrological Institute in St. Petersburg.
On Thursday, April 27, at 2 p.m., Schindler and Shiklomanov will give public lectures at the Davidson Conference Center at the University of Southern California, which administers the prize.
On Friday, April 28, at 7 p.m., the Tyler Prize executive committee and the international environmental community will honor the recipients at a banquet and ceremony at the Four Seasons Hotel in Beverly Hills.
In a series of landmark experiments during the 1970s and 1980s, Schindler showed that acid rain could begin destroying freshwater lakes at far lower levels than previously thought, and that phosphorus was the major cause of eutrophication, or uncontrolled algal growth.
Schindler's data had a decisive influence in the policy wars over sulfur oxide emissions and phosphorus use.
"His experiments were key to the ban of phosphorus in detergents and to the understanding of the impacts of sulfuric acid in lakes," wrote Wallace Broecker, professor of earth and environmental sciences at Columbia University, in his nomination letter.
Peter Vitousek, professor of biological sciences at Stanford University, compared Schindler's approach - the fertilization of whole lakes in a Canadian research reserve - to inconclusive studies by other scientists.
"Dave Schindler did the right set of experiments ... demonstrating beyond any reasonable doubt that P (phosphorus) controls the eutrophication of temperate lakes," Vitousek wrote.
"Dr. Schindler then took the same approach to the issue of acid rain. Other people did good work on acid rain effects - and some of them spent a great deal more money - but none of them provided such clear, convincing information," Vitousek added.
Schindler's skill as a scientific communicator has earned him influence in the policy arena, according to Karen Kraft Sloan, a former member of Canada's parliament.
"His words are used time and time again as the highest measure of credibility to educate the public on an issue or to get the attention of parliamentarians and the government," Sloan wrote.
Schindler continues to study the effects of external factors on freshwater bodies, focusing on climate change, alien fish species and cumulative effects of human activities.
While Schindler studied global pressures on small ecosystems, Shiklomanov researched small pressures on global water supplies.
He is best known for describing the connection between millions of local water withdrawals and the world's water "budget."
In his highly regarded 1974 paper, "Global water balance and water resources of the Earth," Shiklomanov published the first global estimate of renewable freshwater withdrawals. Around the same time, he estimated total freshwater consumption from 1900 to 1970, discovering a sharp increase beginning after World War II.
Further research over the next 20 years led to the study, "World Water Resources at the Beginning of the 21st Century," in which Shiklomanov predicted disastrous results in some parts of the world if the trend of massive dam projects and large-scale irrigation continued.
Instead, Shiklomanov presented an alternative model of water use that would stabilize water consumption and eliminate shortages in many regions.
"A more fully developed version of his sustainable development scenario has recently been worked out and is being used by various [United Nations] agencies as a guide for future developmental projects," wrote Z. D. Kopaliani, vice chairman of the State Hydrological Institute in St. Petersburg.
"His work is of utmost importance for a balanced world development in the next few decades," wrote Malin Falkenmark, senior scientist at the Stockholm International Water Institute. "It is only by understanding similarities and differences between regions and by revealing where the current trends [are] bringing humanity that the water crises towards which we are now heading can be identified well in advance.
"The importance of the work can be judged from the fact that he is seen as the central world authority in this field."
The Tyler Prize for Environmental Achievement is one of the premier awards for environmental science, energy and medicine.
It was established by the late John and Alice Tyler in 1973 and is awarded annually to individuals associated with world-class environmental accomplishments.
For more information on the Tyler Prize, visit www.usc.edu/dept/LAS/tylerprize.