over which states maintain discretion, he said. Expecting such a challenge, however, EPA outlined in its proposed rule why nonpoint source pollutants fall under its regulatory authority. "EPA believes that from the time we first talked about the 303 listing, we've never separated point or nonpoint pollutants at the source. We've always focused on impaired water bodies, so [regardless of whether] impairment comes from one source or another, EPA has always said it should be listed " Brady said. Although the proposal will spur increased interest in nonpoint pollutants, no new limits are likely to follow, Brady emphasized. "While a TMDL may quantify or clarify loadings from agricultural sources or those resulting from air deposition, existing controls would be used to try to attain those allocations." But, bringing nonpoint sources into the program could affect the way states conduct land-use planning, according to an environmental attorney close to the debate. Under the statute, before additional pollutants can be
added to a water body, a TMDL has to have been established, which translates into no growth. In addition, under a companion rule amending the National Pollutant Discharge Elimination System {Fed. Regist. 1999, 64 (162), 46,057-46,089), EPA outlined a trading program for water pollution credits that could stunt new growth. The provision would require dischargers seeking to expand their facilities, as well as all major new dischargers to offset additional discharges on a 1.5 to 1 ratio The big question remains, however, whether the proposed rules would succeed any better than existing regulations in getting remaining polluted waterways cleaned up. Past barriers to effective TMDL implementation included tight state budgets, a lack of monitoring data, and the difficulty of tracking down nonpoint source pollutants. "We're concerned that we couldn't possibly implement it because we just don't have the hundreds of people and milliondollar budget that it would take to do it," said David Word, assis-
tant director of Georgia's Department of Environmental Protection and acting chair of the Environmental Council of States water committee. His department is currently under a court order to develop TMDLs for all the state's water bodies within seven years after losing a lawsuit filed by the Sierra Club. "I think the whole TMDL process is fundamentally flawed, and it's going to present a lot of difficulties until there are achievable [water quality] standards " he added explaining that most streams on Georgia's 303(d) list are there because of fecal coliform violations Even undeveloped areas violate fecal coliform limits hpraiise of wilrl animals lurincr ttiprp t i e Qnid
Ultimately, however, the program's success "won't be judged by the sheer number of water bodies identified or even the number of pollution limits adopted, but whether the states and EPA will vigorously implement and enforce any final rules for each specific water body," said Mark Izeman, senior attorney for the Natural Resources Defense Council. KRIS CHRISTEN
Mapping carbon content stored in world's forests A project to map global vegetation cover could answer one of the most burning questions in global warming predictions—namely, how much carbon is locked up in the earth's forests, according to researchers from the University of Maryland-College Park (UMD) and the National Aeronautic and Space Administration (NASA). To determine the world's biomass, lidar-sensing equipment will be launched on a satellite in September 2000 as part of NASA's Earth System Science Pathfinder project. From an orbit about 400 kilometers above Earth, the Vegetation Canopy Lidar (VCL) mission will probe the forest canopy by firing rapid pulses of laser energy at the Earth's surface from five near-infrared wavelength laser beams. The reflected wave forms will reveal where foliage trunks and branches are concentrated in the space between the ground and the tree toDS
The VCL will characterize the vertical structure of the Earth's forests including tree heights to an accuracy of better than one vertical meter, all the branches and leaves of the canopy, and ground surface topographic elevations below the forest canopy, said Ralph Dubayah, an associate professor in UMD's Geography Department and the project's principal investigator. He added that this information has never been known before to any degree o f 3CC11T3CV
Data gathered from the 18month mission should help clarify how land-use practices, such as deforestation, are affecting the world's climate. One-half of a tree's biomass is carbon, so "when we burn or cut down trees, this carbon goes up into the atmosphere as carbon dioxide," Dubayah said, noting that the amount of CO added to the atmosphere through deforestation
is a significant fraction of the total from human activities. The VCL data also could enhance monitoring under the Kyoto Protocol, improve weather and climate modeling, and offer crucial information for biodiversity studies and forest management. —KRIS CHRISTEN
DID YOU KNOW? Greenhouse gas: Once released into the atmos phere, sulfur hexafluo ride (SF6), the moss potent greenhouse gas known, has an atmospheric lifetime of about 3200 years. Source: ES&T 1998, 32120), 3077-3086).
NOVEMBER 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 4 4 7 A
