Oil Spills Pollute Indefinitely and Invisibly

The Prestige oil tanker, carrying 76 million litres of fuel oil, sank off the northern coast of Spain in November 2002, releasing at least 3 million litres of oil into the waters of an extremely rich fishing region.

A report published earlier shows that in sensitive near-shore environments, the effects of an oil spill can be seen even decades later.

The findings come from a study of the aftermath of an accident that occurred in Buzzards Bay, Massachusetts, on a foggy morning in September 1969. A Boston-bound barge entering the Cape Cod Canal ran aground on rocks, spilling 700 000 litres of diesel fuel into the bay. The Prestige sank in waters that are more than 3,2 kilometres deep, about 241 kilometres off shore. Still, so far, more than 241 kilometres of beaches and coves have been fouled.

Evidence from the Buzzards Bay disaster suggests the effects of oil spills could be indefinite. Thirty years after the Massachusetts catastrophe, significant oil residues remain in local salt marsh sediments. It is clear from this study that oil spills can have a long-term impact on a coastal environment, marine chemists say.

Even after all these years, concentrations of some compounds (in at least one Buzzards Bay site) are similar to those observed immediately after the spill, and reflect the persistent nature of the oil in coastal salt marsh sediments.

Parts of Buzzards Bay were heavily contaminated by the brown, viscous oil. Fish, worms, crabs, molluscs, and other animals perished in great numbers, along with oil-smothered marsh grasses. Residents of the nearby town West Falmouth, referred to the following months as the "silent fall", referring to the absence of the usually noisy grasshoppers, waterfowl, and other animals normally in the area.

At the time of the accident, researchers assumed that oil would be naturally dispersed within a few months or years. However, surveys during the 1970's and in 1989 detected oil in marsh sediments providing strong evidence that this isn't always the case. Oil slick might disappear as far as visual sighting on the surface of the water, but petroleum hydrocarbons could still persist in sediments.

To study the consequences of the incident with Prestige oil tanker scientists collected a 36-centimetre-deep sediment core from the marshes impacted by the spill. The core was divided into small sections – less than 2 centimetres – and tested for the presence of oil.

The results confirmed that despite the otherwise pristine appearance of the marsh, oil residues remained. The team found no contamination in the first 6 centimetres of the sand and earth sample. However, the central section of the
core, retrieved from 6 to 28 centimetres below the surface, contained diesel oil compounds.

Oil that has decomposed in the environment should show a different mixture of petroleum compounds to fresh oil, scientists say. However, many typical diesel oil compounds were observed in the core sample. This suggests that the oil degraded very little over time. Bacteria and Mother Nature have not significantly weathered the oil.

In addition, some of the chemicals in the sample core were at the same high concentrations found directly following the 1969 accident.

At the time of the spill, scientists doubt many people would have been able to predict the oil was still present after 30 years. But the study shows that oil can last for a long time, and is important when assessing the fate and clean up of future spills.

The reason for the oil's persistence at this site could be due to the lack of oxygen or sulphate compounds in marsh sediments, which many oil-decomposing bacteria need to survive. Thus, the findings confirm what many scientists suspected: deeply penetrated oil in oxygen depleted marsh soil persists for long times. These results are helping understand the long-term fate and persistence of oil in these sensitive habitats

The next question is what are the ecological consequences of this long-lasting contamination?

John Pickrell. National Geographic. 2002

China's Dust Storms Raise Fears of Impending Catastrophe

In 2001 an unusually large dust cloud that originated in northwest China drifted across the continental United States and lingered over Denver and other areas, at times obscuring views of the Rocky Mountains.

It isn't the first time a giant dust cloud from East Asia has reached the United States. But concerned observers say the vast sweep and the density of this latest one suggest that northwest China's once-fruitful agricultural land is eroding at an alarming rate, becoming useless desert.

China has mounted various efforts to halt the increasing desertification, which is caused by overuse of the land for farming and grazing. Nonetheless, as much as 2 300 square kilometres of farmland in northern China – an area more than twice the size of Hong Kong – is blown away by the wind each year.

East-moving winds often carry soil away from China's northwest, where overplowing and overgrazing, coupled with periods of drought, has led to massive deterioration of the country's agricultural resources. Huge dust plumes regularly travel hundreds of miles to Beijing and other cities in northeastern China. As they move over urban centers they pick up particles from industrial pollution.

The resulting dust clouds are often so thick that they obscure the sun, reduce visibility, slow traffic, and close airports. Residents caulk windows with old rags to keep out the dust, and municipal crews have to clean public structures repeatedly during the dust-storm season.

The growing severity of the dust clouds has raised world concern. The dust clouds are also a problem for China's neighbors – North Korea, South Korea, and Japan have registered official complaints. Responding to pressure from their citizens, legislators from Japan and South Korea are organizing a tri-national committee with Chinese lawmakers to devise a strategy to combat the dust.

Ironically, the rapid deterioration of China's cropland has resulted in part from programs aimed at increasing agricultural output. Decades of reforms have included measures that removed limits on the amount of land that farmers could cultivate and the size of herds and flocks they could maintain. As a result, the demand for land has soared. Fast-growing coastal provinces are also losing much cropland to urban expansion. The big risk is that it is going to push a lot of people into cities in a major migration.

Now accelerating wind erosion of soil and the resulting land abandonment are forcing people to migrate eastward. In some areas the land has been rendered so useless that farmers have abandoned their homes and fields, which are now covered with wind-blown sand dunes. Where farming is still practiced, some reports indicate that typical yields of crops such as potato, rice, and corn have shrunk dramatically, making harvests no longer profitable.

Adding to the direct damage to soil, the northern half of China is becoming drier and sources of natural irrigation more scarce. Temperatures in the region have been hotter than average in the past 10 years, and aquifers are being depleted by overpumping. U.S. satellites, which have monitored land use in China for three decades, show that thousands of lakes in the north have disappeared. And rapid industrial development has reduced forests and other vegetation that once provided moisture to the region.

Scientists say that desertification has become a bottleneck for the social and economic development and the improvement of people's living standard in some areas of China.

Reggie Royston. National Geographic New. 2001

Is Acid Rain Killing Off Wood Thrushes?

Acid rain may be forgotten, but it is not gone, and now ornithologists have linked it to the decline of the wood thrush, a forest bird known for its beautiful song.

The wood thrush breeds in the eastern United States and southeastern Canada, and winters from central Mexico to Panama. Like many neotropical migrants, its population has been declining – nearly 2 per cent a year between
1966 and 2000, according to Breeding Bird Survey (BBS) data compiled by U.S. and Canadian wildlife agencies.

The researchers did a statistical analysis and found that increased amounts of acid rain make wood thrushes less likely to breed. Ecologists were surprised to uncover a negative effect this big because like many people, they thought acid rain was a non-issue.

Despite rising awareness of acid rain's more insidious effects, such as calcium depletion in soil, research on declining populations of North American birds has continued to focus on the dangers of habitat loss and fragmentation. Indeed, it is the first time in North America when the finding has linked large-scale evidence of the population decline of a land bird to acid rain.

The situation is reversed in Europe, where, perhaps owing to centuries of habitat fragmentation, researchers have been looking at more immediate threats: industrialized farming practices and pollution, including acid rain. Their studies of calcium depletion raised a number of red flags that may apply to the wood thrush.

Acid rain, for example, can cause calcium to leach from the soil. The loss of this nutrient jeopardizes the breeding success of birds – to produce a clutch of eggs, a female bird may require up to 15 times more calcium than a pregnant mammal of equivalent size.

In areas where acid rain is most severe, the supplementary calcium-rich foods that female songbirds depend on – snail shells, isopods such as pill bugs, millipedes, and earthworms – may be in short supply. Lacking adequate calcium in their diet, females are more likely to lay eggs that are thin, brittle, and porous. If the weakened eggs can withstand the rigors of incubation, the parent birds will be hard-pressed to meet the very high calcium requirements of their growing nestlings.

Aside from depleting calcium, acid rain in soil can promote increased levels of potentially toxic aluminium, cadmium, and lead. Polluted soil, moreover, may slow the decomposition of leaf litter, which reduces the diversity and abundance of prey.

Now it is crucial for scientists to understand the process that leads to these effects. The findings regarding the wood thrush are correlational. To get down to exactly what is going on more focused studies are needed.

Robert Winkler. National Geographic News. 2002

India's Black Market in Birds Threatening Rare Species

India is home to some 1,200 different species of birds. Despite measures designed to protect this rich array of bird life by banning the capture and trade of wild birds, records indicate that as many as 300 of these species are caught and
traded with impunity. Large seizures of illegally captured wild birds in India number about 30 each year. In one of the largest recent incidents illustrating the huge scale of this flourishing black market, more than 10,000 birds were confiscated at the Mumbai (formerly called Bombay) international airport in March 2001.

Until 1991, India was one of the largest exporters of wild birds to international bird markets. Most of the birds traded were parakeets and munias, especially the rose-ringed parakeet, the black-headed munia and the red munia. In 1991, however, an amendment to the Indian Wildlife Protection Act of 1972 was adopted that bans all trade and trapping of indigenous birds in the country.

However, the ban is ineffective, as illegal bird trade flourishes in almost all cities, towns, and rural hamlets of the country. The trade is not limited to domestic markets. There is continuous large-scale bird smuggling out of the country. A number of the wild birds on the Indian subcontinent that are being widely traded are threatened species, including the swamp francolin, green munia, Finnâs baya, and Shaheen falcon. Of the many different species being traded, 16 are among the world's most highly endangered, 36 are listed in the Convention on International Trade in Endangered Species (CITES), and six are included on the Red Data list of endangered species compiled by the International Union for the Conservation of Nature and Natural Resources (IUCN).

Wild birds are captured for at least seven reasons, which helps explain why the practice is so prevalent and difficult to halt.

Besides the usual practices of trapping birds as pets and for food, zoological and medicinal purposes, or taxidermy, several species of birds that are poor candidates as pets and for consumption are often captured for the bird-release business.

This is a uniquely Indian religious tradition. Among Hindus, Jains, and a few other communities, there is a belief that releasing birds that are held in captivity can purify the soul and relieve personal sins. On auspicious days, people go and buy birds from traders for release. This has led to the development of an entire business around the religious custom. Species of wild birds that are unsuitable as pets or food are captured and brought near these holy places for the devout to purchase and re-release.

Some important protected species like the horned owl were hunted for black magic rituals and sorcery, such as the practice of certain tribes that use the owls to purify "amulets" during their street performances.

Finally, although the sport of falconry is now a vanishing art in India, a large number of wild raptors are caught every year to smuggle to the Middle East, where falconry is still popular.

Accurate figures on the capture of wild birds for local consumption are impossible to obtain because of the secretive nature of the practice. It is known, however, that species ranging from pelican to ducks and waders are caught for
consumption. Added to these huge losses is a large number of bird deaths during international transit. For every bird that reaches its final destination, two die en route. The mortality of wild birds during transit is thought to have increased since the trade ban was put into effect because of the extra efforts that are made to conceal the illicit cargo.

Pallava Bagla. National Geographic News. 2002

"Dirty Fishing" Emptying Oceans

In June 2003, along the shoreline of Mauritania, in northwest Africa, scientists made a gruesome discovery: the carcasses of 230 dolphins, a pilot whale, and 15 endangered hawksbill and leatherback sea turtles. Because of the mixture of species found, and the fact that some of them were entangled in sections of fishing nets, it is likely that these animals were killed as bycatch.

Across the world's oceans, large commercial fishing boats haul aboard huge nets and 97-kilometre lines teeming with unwanted creatures – bycatch, sometimes referred to as "bykill" or "dirty fishing". "Bycatch is a mix of young or low-value fishes, seabirds, marine mammals, and sea turtles, often considered worthless and tossed overboard – dead or dying. The collateral damage amounts to about 30 million tons of sea life each year – about one-third the total global catch. Among the worst offenders are shrimp trawlers, who often discard up to 10 pounds of sea life for each pound of shrimp they catch.

Just 10 per cent of swordfish, sharks and other large, predatory fish remain in the world's oceans after just 50 years of commercial fishing. Without immediate action, they could go the way of the dinosaurs.

Bottom trawling inflicts the most damage on the undersea environment. Trawlers drag weighted nets up to a quarter-mile wide along the ocean floor, bulldozing deep-sea coral reefs and other seafloor ecosystems where many sea animals live or breed. It is the equivalent of clear cutting forests to hunt deer.

The study also classified gill nets and longline fishing as "high impact". With these methods, you're catching and killing everything that swims by. Gill nets are transparent fences, suspended by top floats and stretched taught by a weighted bottom. Longlining – one of the most common fishing methods – sets out miles of baited hooks that snag or entangle unwanted species, including at least forty seabird species.

The enormity of the problem still isn't understood. All seven species of marine turtle are endangered. The rarest turtle, the leatherback, has declined by 95 per cent oceanwide. With better-protected nesting beaches, scientists believe bycatch plays a big role in population declines.

Fisheries around the world kill seals, whales, dolphins, and other marine mammals in the course of operations. Some of these are endangered species.
The bykill issue is a huge, complex problem. There is no one-size-fits-all solution. Bycatch must be addressed, fishery by fishery.

Some types of gear, like purse seines and hook and line are less damaging.

In some cases, the answer is to modify gear. For example, in the Bering Sea, changing net's mesh size and shape cut bycatch of young pollock by 75 per cent.

An abiding success is the dolphin. During the 1960's, 200,000 dolphins a year drowned in drawstring nets used for Pacific yellowfin tuna. Public outcry and a consumer boycott spurred Congress to pass the Marine Mammal Protection Act in 1972. Since then, nets are set to spare dolphins.

Another lifesaving technique is to outfit gill nets with acoustic alarms called "pinger," which reduced capture turtles greatly.

The world's largest flying bird, the wandering albatross, is in serious trouble because of longline tuna fishing in the sub-Antarctic Ocean. But an innovation by Japanese fishermen is keeping birds away from some operations. They attach metallic red streamers to nets that scare the birds away while nets are submerged.

Growing scientific evidence shows that some marine species are threatened with extinction – and others will be – unless fishing practices and regulations change.

Sometimes the only answer is to limit fishing. Fisheries have been closed where populations are "economically extinct", like the North Atlantic cod fishery.

Recent Pew Oceans Commission recommendations call for a new approach to managing fisheries that preserves habitat in addition to setting catch limits. There must be set aside a network of fully protected marine reserves, linked by corridors, to protect breeding and nursery grounds.

The bycatch issue requires both national regulations and international agreements. Regulations can save species. One conservation success is Kemp's ridley turtle, once the most endangered marine turtle. By the 1970's, shrimpers in the Gulf of Mexico had fished them nearly to extinction. Only 300 nesting females remained. Then in the mid-1980's, the Turtle Excluder Device, or TED, a turtle escape hatch, was introduced. Since 1990, TEDs are required in U.S. waters, though compliance varies by region. Today, nesting females have jumped to 3,000.

Given a measure of protection, sea creatures can rebound.

Sharon Guynup. National Geographic Channel. 2003

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