It's easy to make too much of academic debate, especially from the standpoint of those managing natural resources in the field. I will try to focus my review on points that might interest a manager.
The authors of the original article, ``Uncertainty, resource exploitation, and conservation: lessons from history,'' are Donald Ludwig, Ray Hilborn, and Carl Walters. Ludwig and Walters are in the University of British Columbia's Zoology Department; Ludwig is also in the Department of Mathematics. Hilborn is in the University of Washington's School of Fisheries.
The article cited several examples of overexploitation of natural resources, primarily failures to manage marine fisheries for "maximum sustained yield," a yield that often proved to be maximum but rarely proved to be sustainable. The authors' conclusion was that ``...resources are inevitably overexploited, often to the point of collapse or extinction.'' They cited four reasons why overexploitation was inevitable:
When problems arise, managers shouldn't wait for scientific consensus before taking action to correct them. ``Calls for additional research may be mere delaying tactics,'' the authors caution.
While managers should rely on scientists to recognize problems, they should not expect scientists to solve them. Scientists are often tied to a specific discipline, but the solutions to resource overexploitation are likely to be found in interactions involving many disciplines, the authors explain.
Because past attempts at sustainable management have seldom succeeded, any claims of sustainability should be suspect. Nor were the authors impressed by the call of leading ecologists for basic ecological research in the Sustainable Biosphere Initiative. That initiative identified 55 key research topics, none of which involved human population dynamics or patterns of resource use.
Such research may lead to a false complacency, the authors warn: ``...instead of addressing the problems of population growth and excessive use of resources, we may avoid such difficult issues by spending money on basic ecological research.''
So far, the authors' argument may sound like the sort of complaints managers often lodge against scientists. But the authors are scientists themselves. And several of the respondents point out that the authors should have been careful not to generalize from the lessons of overexploitation of marine fisheries.
Indeed, failed resource management policies sometimes trigger a sudden increase in understanding, a redesign and expansion of policy, and renewed flexibility and innovation, points out C.S. Holling from the University of Florida's Zoology Department. He cited the Everglades of Florida, the forests of New Brunswick, the estuary of Chesapeake Bay, the Great Lakes, and the Baltic Sea as areas where resource management policies had improved after notable failures.
Nor should examples from fisheries be generalized to the resources most important for sustaining human civilization such as soil, freshwater forests, atmospheric composition, and some level of biodiversity, write Paul Ehrlich of Stanford University's Center for Conservation Biology and Gretchen Daily of the Energy and Resources Group at the University of California, Berkeley. For these important resources, the sustainable rates of use or destruction are known at least approximately and research promises a substantial reduction of uncertainty.
It would be just as easy to cite examples where scientific information had played an important role in guiding wise decisions as to cite examples where science had failed, write Louis Pitelka of the Electric Power Research Institute in Palo Alto and Frank Pitelka of the Museum of Vertebrate Zoology and Department of Integrative Biology at the University of California, Berkeley. One encouraging example is the response to the depletion of stratospheric ozone, including the discovery and acceptance of new scientific information and the signing of the Montreal Protocol, they write. Another is the effort to involve all stakeholders in developing plans to manage resources (including fish) in the Pacific Northwest.
Science made a difference in preventing overexploitation of sea turtles by shrimp trawling. Shrimpers argued against rules requiring their nets to have turtle-excluder devices. The argument was at an impasse when the Congress sought the advice of the National Research Council, writes David Policansky of the Council's Board on Environmental Studies and Toxicology. A committee that examined all the available data concluded that shrimping killed more turtles than all other human causes combined, perhaps 10 times as many. ``The committee's conclusion was unanimous and its analyses were compelling: scientific consensus was reached,'' he writes. ``Revised regulations are now in place to protect sea turtles and the debate now seems to be focused on the social and economic effects of management actions, rather than on the underlying science.''
A wetland ecologist reviewed her own efforts to improve wetlands over the past two decades to see if she had prevented irreversible damages. ``Regrettably, I found no clear evidence of success,'' writes Joy Zedler, of San Diego University's Pacific Estuarine Laboratory. Still, she could point to one example where science had made a difference. The city of San Diego planned to build a sewer pump station where it would cover the most abundant colony of a rare annual plant, the salt marsh daisy, Lasthenia glabrata. The city agreed to reduce the size of the construction pad and move it slightly.
``Scientific documentation was the critical factor in forcing the redesign,'' Zedler writes. ``Talking about sensitive plants at the construction site had little effect.... The official monitoring reports were doubly important in this case, because the plant is a winter annual and was not visible during our discussions with the City. Annual plants share this problem with rare birds, mammals, and insects. Unless they happen to be on site at the time of controversy, historic records of their occurrence and habitat dependency are essential.''
While sustainable exploitation of natural resources might be difficult to achieve, sustainability is a valuable goal. ``I believe sustainability of biodiversity is a useful target and that research aimed at sustainability is essential even if the results fall short of the mark,'' Zedler writes. Kai Lee of Williams College's Center for Environmental Studies compares sustainability to liberty: ``Sustainability is a goal like liberty or equality; not a fixed endpoint to be reached but a direction that guides constructive change; the realist is as skeptical of claims concerning sustainability as she would be of a claim that perfect liberty had been attained.''
Arguments about the usefulness of science in natural resource debates may be different in developing countries than in North America. ``There are many countries where there is a need to develop a basic level of scientific knowledge and to finance scientists to work on the ecological bases for sustainable resource use,'' writes Eduardo Fuentes of the Catholic University of Chile's Department of Ecology. In addition, it may not be necessary to determine the sustainable level of exploitation if unsustainable levels can be identified. ``...We should concentrate on defining the borders of a sustainability space by scientifically discarding what can be shown to be nonsustainable if continued for a long time,'' Fuentes writes.
The authors of the original article elaborated their ideas in two additional articles. Ludwig points out that overexploitation hasn't been confined to marine fisheries. A 1988 study of forest management in 12 countries concluded that ``...wastage of publicly owned natural forests has been widespread and long standing, often as a result of governmental policies that sought to develop infrastructure and maintain employment.''
For both fisheries and forest resources, sustainability is likely to be sacrificed if the goal is maximum sustained yield. ``Especially during favorable periods for the resource,'' Ludwig writes, ``it may appear that there is a surplus that can increase the yield and thereby come closer to the maximum. The temptation to increase the yield at the expense of additional risk to the resource is often irresistible.''
Sustainable forest management can be especially difficult if landowners can earn more money by cutting trees and putting the money in the bank than by letting trees grow. ``...Trees may grow faster in bank accounts than they do in the woods,'' writes Kai Lee. ``That is, harvesting populations at unsustainable speed, mining the resource, can be rational if the earnings from harvest produce financial assets whose value appreciates more rapidly than the resource would regenerate.''
Forced scientific ``consensus'' may play a perverse role in policy debates, write Marc Mangel, Robert Hofman, Elliott Norse, and John Twiss, Jr., all of whom are interested in the preservation of marine mammals. ``Instead of telling policy makers that they cannot accurately predict the consequences of alternative management strategies, scientists allow themselves to be forced into negotiated agreement,'' they write. ``In hindsight, the consequence of attempting to reach a consensus is clear: one stock after another of the world's large whales have been driven to economic and near biological extinction.''
Part of the problem is society's demand for certainty. ``As they are currently set up, most environmental regulations, particularly in the United States, demand certainty, and when scientists are pressured to supply this nonexistent commodity there is not only frustration and poor communication, but mixed messages in the media as well,'' writes Robert Costanza of the University of Maryland's International Institute for Ecological Economics, Center for Environmental and Estuarine Studies. ``...The real challenge is to develop scientific methods to determine the potential costs of uncertainty, and to adjust local incentives so that the appropriate parties pay this cost of uncertainty and have appropriate incentives to reduce its detrimental effects.''
Society needs to shift the burden of proof in resource management debates if exploitation is to be sustainable, write Mangel, Hofman, Norse, and Twiss. ``To maintain biological diversity and options for a sustainable future, societies need to shift the burden of proof from demonstrating that ongoing or planned activities will damage or destroy the resource and have adverse socioeconomic consequences, to demonstrating that ongoing and proposed use will not reduce management options 15-20 years hence.''
Still, Ludwig is concerned that resource managers may be resorting to ``magic,'' substituting the word sustainability for the reality. ``As long as human desires are unlimited, we shall invent magical theories in an attempt to reconcile the irreconcilable,'' he writes. If sustainability is to be more than a magic word, he feels it is essential to: