As this is the season of giving, here is a gift, a riddle:

Imagine a fast-growing weed is taking over a pond. The weed grows so quickly that the area it covers doubles every day. In fact, within 30 days, the weed will cover the entire pond, suffocating all other life. Local residents recognize that something should be done to prevent the collapse of the ecosystem, but they do not know exactly how fast the weed is growing, nor do they know how long it will take to solve the problem. Assuming corrective action may take several days, they decide to act as soon as the weeds cover half of the pond. On what day will that be?

In many ways, this riddle is an appropriate analogy for viewing today’s environmental challenges. From pollution to resource use, global society is concerned, and watchful, but lacking much of the information it needs to make informed decisions. When a problem is looming on the horizon, how long is it prudent to wait before taking action?

Competition for catch among the world’s fisheries is one example of just such a puzzle. What should we do and when? Dr. W.M. von Zharen of Texas A&M University, writing in Natural Resources and Environment magazine (Summer 2000), describes the problem this way:

“The turf battle centers on too many fishers and too few fish . . . For nearly half of the world’s 6 billion people, seafood is the main source of protein. United States’ consumption of fishery products was [33 kg] of edible meat per person in 1998; in that year U.S. consumers spent an estimated $49.3 billion for fish products. Sea life also provides a source for myriad other commercial products and medicines.

“This quest to catch as catch can, as fast as we can, has resulted in somber statistics: 70 percent of the world’s major fish species are either fully or over-exploited, and that figure increases to 80 percent in U.S. waters. Little wonder there is discontent over which fish belong to whom.”

In Asia, the problem of overfishing is equally dire. At an international symposium on protecting and managing coastal marine ecosystems held in Bangkok earlier this month, one marine expert warned that 60 percent of people living in the Asia-Pacific region live along the coasts and the resources they depend on are “deteriorating at an alarming rate.”

Hugh Kirkman, a U.N. Environment Program marine specialist, reported that two-thirds of the major fish species and several of Asia’s most important fishing areas are fully- or over-exploited. “Sixty percent of the fishing fleet could be removed and the same number and volume of fish would be caught.”

Now back to the riddle. If the weeds double every day, then the pond will be half covered with weeds on the 29th day, just one day before completely overtaking the pond. If the local residents wait until the pond is half covered before taking action, they will have just one day to respond. Too little time to act wisely and in the best interests of the ecosystem, and those who depend on it.

Applying this analogy to environmental issues in general, the challenge becomes how to respond well in advance of the 29th day. Concerning fisheries, the question is how to deal with overfishing before fish populations collapse and become “commercially extinct,” meaning there are no longer enough fish to warrant the extraordinary efforts it would take to catch them.

Unfortunately, fisheries are already in a critical state. In fact, anyone scanning this newspaper over the past several weeks would be justified in believing fisheries have already hit their 29th day, if desperate measures are any indication.

In mid-December, according to an AFP-Jiji news service piece, South African Environmental Minister Valli Moosa declared a moratorium on two species of fish and cut quotas by 80 percent on 16 other species. The report stated that all 18 of the species have been classified as “collapsed,” meaning less than 25 percent of the species’ breeding stock is left.

A few days later, AP reported that European fisheries ministers had agreed to cut catch quotas for 2001 by as much as 50 percent to protect species in European waters that are on the brink of commercial extinction.

Biologists have seen this coming for years, if not decades. More and larger boats venturing further from shorelines and advances in fishing technology have kept catch levels high, even as fish populations have been declining.

Not surprisingly, with more and more boats sweeping the seas, fishers catch and sell whatever they can. As McGinn points out in Worldwatch Paper 142, “Rocking the Boat” (1998), “Fishers haul in species at a younger age and smaller size. . . . Targeting young fish undermines future breeding populations and guarantees a smaller biological return in the coming years. . . . Consumers are essentially ‘eating the babies.’ “

Clearly Japan has a great stake in the survival of fisheries. As Hiroya Sano, president of the Japan Fisheries Association, points out, “the Japanese people are the largest consumers of fishery products in the world.” Neither JFA nor the Japanese government, however, supports Draconian measures. In an opinion written last year regarding southern bluefin tuna (see Web site below), Masayuki Komatsu of JFA states, “The best approach to marine living resources is not extreme protectionism or a ban on fishing.”

Tuna is of particular concern to Japanese fishers. Fearful that other nations may call for a ban on species that are overfished, Japan’s tuna fishing industry, with the support of the central government, recently established the Organization for Promotion of Responsible Tuna Fisheries. The goal of OPRTF will be to eliminate “illegal, unregulated, unreported” tuna fishing operations that target the Japanese market.

With cooperation and restraint, legitimate fishers may be able to clear the seas of IUU vessels before the waters are cleared of tuna. Nevertheless, with some fisheries collapsing and others on the brink, ensuring a sustainable future for fisheries may indeed require extreme measures, including a temporary ban on catching certain species.

Whether today is the 19th day of the fisheries crisis, or the 29th, the “Precautionary Principle” remains the wisest course of action for dealing with ecosystems and resources. The rule, found in Principle 15 of the Rio Declaration, states, “In order to protect the environment . . . where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.” Simple but wise words to live by for fishers, farmers, states and corporations, not to mention for families, friends and in-laws at the holidays.