The sixth extinction: throughout the 4.7 billion-year history of Earth life forms have vanished, usually because they couldn't adapt to a changing environment. (Biodiversity).

Earth's environment has always changed, usually slowly. As the environment changed so too did the life forms it supported. Some adapted to the new world by evolving to take advantage of the new conditions. Others, that were not able to adjust, simply perished. These extractions took place over long periods of time. However, five times during the history of our planet mass extinctions have taken place.

A wobble in Earth's orbit or a strike by a large meteorite have caused the climate to heat up or cool down. In geological terms, these climate changes happened rapidly over the course of a few thousand years. Life forms used to cool weather wilt and die off if the average temperature rises quickly; tropical plants freeze and expire if touched by frost:

* 440 million years ago trilobites died off when the sea level dropped because Earth's temperature fell;

* 370 million years ago a period sometimes called The Age of the Fishes came to an end when a sudden event wiped out about 19% of species;

* 250 million years ago, during the Permian geological period, the Earth warmed up and 54% of species marched off into extinction;

* The Triassic period was generally hot and reptiles were the dominant life forms, but another rapid climate change killed off about a quarter of the species;

* The best-known mass extinction happened about 65 million years ago when about 17% of the species thought to have existed, including the dinosaurs, disappeared.

Now, there are fears we are at the start of another mass die-off, but this one may be triggered by the activities of just one species--us. Writing in the Globe and Mail, Alanna Mitchell says: "Most of the international scientific community is convinced that the whole planet is on the brink of a mass extinction not seen since the dinosaurs vanished 65 million years ago."

The gloomiest of these scientists predict that about half the species in the world today will have vanished by the middle of this century. There are others, however, who say the threat to the world's many and varied species is nowhere near that catastrophic.

So, who do you believe?

Environmentalists have been known to exaggerate the scale of a crisis in the past. They do this because they depend on donations from the public to fund their activities and people are likely to be more generous if they think a disaster is just around the corner. On the other hand, the corporate world can be relied on to minimize environmental problems. They do this in order to persuade governments not to bring in environmental protection laws that might cut into profits.

The sensible approach is to apply what's known as "The Precautionary Principle." This means working from the assumption that many species are threatened with extraction unless it is proven beyond doubt that they are not.

At present, the evidence available suggests that many species are in danger of vanishing, largely because of human activity.

Some scientists say we belong to what they call the Noah Generation; we have the power to decide whether or not to save certain species.

Of course, we've already made some of those decisions.

The pig-footed bandicoot (Australia), the Bavarian pine vole (Germany), the Arabian gazelle (Saudi Arabia), the pygmy hippopotamus (Madagascar) are just a few of the species of mammals that have disappeared from the wild over the last several decades. These animals were lost because their habitat was destroyed by humans.

The World Conservation Union, based in Switzerland, says life forms are threatened on every continent and in every form of habitat. Almost 1,000 species are in danger of vanishing in the United States. Malaysia is home to 805 threatened species, Indonesia 763, Brazil 608, and so on down the list. The small Pacific Ocean island of Tonga has 10 threatened species and the large Indian Ocean island of Madagascar has 302. Even in the Antarctic, some forms of life are clinging weakly to existence, while in Canada 52 species, including 14 mammals, are close to disappearing forever.

With the exception of the United States, the problem seems to be worst in places where tropical rainforest is being destroyed--the Philippines, Brazil, Indonesia, Indo-Burma, the Caribbean. The heat and humidity of the rainforest has encouraged a very rich diversity of life forms to develop. A rainforest may have 300 species of tree, whereas a similarly sized area of natural Canadian forest may only have five to 12. So, whacking down a hectare of trees in South America is going to take out way more species than destroying a hectare of sand in the Sahara Desert.

As the rainforest is such a rich source of biological diversity its continued destruction is especially troubling. Scientists estimate that if the current rate of rainforest destruction continues between 17,000 and 100,000 species will be lost annually in the next few decades.

Probably, the majority of life forms on Earth have yet to be discovered. Deep in the rainforest and deep in the oceans there are vast numbers of plants, insects, fish, crustaceans, and other species that we know nothing about. We have no idea what effect destroying these life forms will have on the rest of the ecosystem.

However, there are more than a few people who ask, so what's the big deal about losing some unknown insects and plants? If most of those species vanish before we even discover them how can this make us worse off? Does it really matter much whether or not Vietnam's warty pig still wanders that country's forests. Maybe the world's a better place now that the Puerto Rican spiny rat is no longer around. These were species we had already discovered and their loss has not impacted the lives of people in Fredericton, or Grande Prairie, or anywhere else.

The problem with this line of thinking is that it ignores one of the fundamental rules of Nature--EVERYTHING IS LINKED TO EVERYTHING ELSE. If one part of the ecosystem is damaged or destroyed, then everything to which it is linked will also be affected. Removing one species leads to the deaths of any other species that feed on it, and removes controls on the growth of any species it fed on. Fragile ecosystems are at risk of collapse from even quite minor environmental changes, whether natural or the result of human activity.

Then, there is our own self-preservation. Around a quarter of all medicines have been developed from plants found in areas of very high biodiversity. And, according to the environmental group Friends of the Earth, 80% of the primary health care of developing countries is derived from forests.

Science does not yet fully understand the biochemistry of any living organism. Every species alive contains dozens of chemicals of unknown but potentially useful function. Multiply this by the number of species and the implications for medicine are obvious.

Meanwhile, Philip Currie has another spin on the threat coming from species extinction. Dr. Currie studies dinosaurs in Alberta's badlands. He thinks the disappearance of these huge reptiles might hold the key to the future of human life on Earth. Dinosaurs dominated the world for more than 150 million years and may have stretched the environment almost to breaking point. Dr. Currie says that, during the last few millions of years of the dinosaur age, species were dying off rapidly. The die-off was the result of species not being able to adapt to a changing climate.

Then, about 65 million years ago, a huge asteroid crashed into Earth. It triggered fires that covered continents and caused vast clouds of carbon dioxide to billow into the atmosphere. This catastrophe was enough to bump off the few dinosaurs that were still clinging to life.

This is where Philip Currie sees a dire warning for humans. If there had been a wide variety of species around when that asteroid crash-landed some of the dinosaurs probably would have survived. But, the ecosystem was already so badly weakened that the collision pushed all dinosaurs over the edge into extraction.

There are strong similarities in today's situation. The environment on which we depend for our existence is already stressed--water is scarce and polluted, soil erosion and desertification are cutting the inventory of arable land, the air is becoming so choked with carbon dioxide that the weather is changing. Biodiversity is also declining. The World Conservation Union says that 24% of mammal species are in danger of extinction. In addition, a quarter of all reptiles, one fifth of amphibians, almost a third of fish, and one-eighth of all birds are at risk.

This, says Dr Currie, is the same set of conditions the dinosaurs faced 65 million years ago. Then, along came an immense force of Nature. Another asteroid might come whizzing out of space. We have enough nuclear weapons stored to bring on a major disaster. Perhaps, there's a terrible disease currently lurking within a rainforest that we are busy clear-cutting. Maybe, the process has already begun in the form of climate change. Apparently, the global warming we are seeing today is more rapid than anything so far detected in Earth's history. Our climate is changing at a faster pace than the catastrophic change that overtook the dinosaurs.

SUGGESTED ACTIVITIES:

1. This article is based on the assumption that evolution through natural selection is a fact. However, many people challenge the validity of evolution and prefer the Biblical explanation for life on Earth i.e. that it has all been created by God. Engage students in a debate on how the content of this article might change if the concept of creationism proved to be correct.

2. Nature's goal is to ensure the survival of the entire ecosystem that is Earth and offers no special guarantees that humans mill always enjoy some sort of exalted position. Organize a debate around this based on the resolution that planet Earth would be a better place if the human species were to become extinct.

3. The Washington Post reported in May 2002 that tiny parasites have been killing bees in the United States; more than 80% of the mild honeybees may already have been lost. One third of food crops in the U.S. re/y on insect pollination. To raise public awareness, beekeepers are using a quotation attributed to Albert Einstein: "If the bee disappeared off the surface of the globe, then man would only have four years of life left." Have a team of students investigate the crucial role of bees in the food system and give a short report to class.

FACT FILE

According to a World Wildlife Fund report in 2000, one third of the world's biodiversity had been lost since 1970.

By studying fossil records, paleontologists have calculated that the normal rate of species extinctions is about one every four years.

Websites

Committee on Recently Extinct
Organisms - http://creo.
amnh.org/index.html

Conservation International - http://www.conservation.
org/xp/CIWEB/home

Friends of the Earth - http://
www.foe.co.uk/campaigns/
biodiversity/

The Olduvai Theory - http://
www.hubbertpeak.com/
duncan/olduvai2000.htm

Red List of Threatened Species
- http://www.redlist.org/

Wildcanada - http://www.
wildcanada.net/new_site/

RELATED ARTICLE: The world in miniature.

Scientists say we can see the future of biodiversity right now in Madagascar. The planet's fourth largest island is home to many unique species of life. Because of Madagascar's isolation from any other landmass, evolution took some unusual twists and turns so that about 85% of its life forms exist nowhere else. That means roughly 170,000 different plants, animals, insects, and other life forms can only be found on this island. Conservation International reports that "More than 80% of the 10,000-12,000 flowering plant species in Madagascar are endemic, in addition to 91% of 300 reptile species. Madagascar also claims 12% of all living primate species. The 33 species of lemur found here exist nowhere else.

But, about 2,000 years ago a new species arrived on Madagascar, and this meant doom for many of the island's original inhabitants. The new arrivals increased in number so that today there are 14 million of them and they are competing with the earlier residents for living space, food, and other resources. They are, of course, people; among the poorest people in the world. In the difficult struggle to stay alive, the people have cut down about 90% of the island's original rainforest. What little is left is disappearing at the rate of 200,000 hectares a year; it might all be gone in a decade. But, what else are the Malagasy people supposed to do? Almost three-quarters of them live on less than a dollar a day. The forest is the only place they can find food and fuel.

There has, however, been some progress towards protecting Madagascar's biodiversity in the past 16 years. New protected parks and reserves have been set up and the World Bank and World Wildlife Fund have negotiated a "debt for Nature" deal. Through this agreement there is funding for some of the government's conservation efforts, and attempts are made to involve local people and provide them with economic alternatives and opportunities.

One of the latter includes a proposal by the Canadian company Rio Tinto to open a mine. However, controversy surrounds this plan. Rio Tinto believes the mine will provide jobs with good pay, and that people who are thus lifted out of extreme poverty will not ransack the forest. Activists with Friends of the Earth claim the mine will destroy the rainforest and local income can be improved by encouraging eco-tourism.

RELATED ARTICLE: Back to the stone age.

Richard Duncan thinks one of the species threatened with extinction is homo sapiens--that would be us. His Olduvai Theory is named after the Olduvai Gorge in east Africa where the earliest Stone Age ancestors of humans have been found. Dr. Duncan says our Industrial Civilization may last only a single century. Worse than that, he thinks that century is already more than 70 years old, having started about 1930. He bases his theory on an analysis of energy production and population growth.

The Industrial Civilization is founded on an intensive use of energy, and the amount of energy produced per head of the world's population grew rapidly from 1945 to 1973. Growth slowed in the 1970s and, according to Dr Duncan, "Then suddenly--and for the first time in history--energy production per capita took a long-term decline of 0.33% per year from 1979 to 1999. The Olduvai Theory explains the 1979 peak and the subsequent decline. More to the point, it says that energy production per capita will fall to its 1930 value by 2030, thus giving Industrial Civilization a lifetime of less than or equal to 100 years.

"Should this occur, any number of factors could be cited as the `causes' of collapse. I believe, however, that the collapse will be strongly correlated with an `epidemic' of permanent blackouts of high-voltage electric power networks-worldwide. Briefly explained: `When the electricity goes out, you are back in the Dark Age. And the Stone Age is just around the corner.'

"The Olduvai theory, of course, may be proved wrong. But, as of now, it cannot be rejected by the historic world energy production and population data."

RELATED ARTICLE: Technogaians.

One group of people is pinning its faith on technology to get us out the mess we have created of our planet. Some are calling these people "technogaians" after "Gaia" the Earth Mother of Greek mythology. They see a bright future in which humans live for 200 years and tiny robots clean up pollution. There will be no cancer and our minds will be uploaded into machines that will exist as long as the planet does. In theory, there will be no more extinctions and even those species that have already vanished will be recreated. Poverty will be banished and hunger eliminated because microscopic nanorobots will create food from the very molecules of the air we breathe. Many of the technogaians can be found in clusters around the high-tech companies of California. They are a strange blend of scientists, mystics, artists, capitalists, libertarians, and others. The future they speak of is only 30 to 50 years away.

RELATED ARTICLE: A decade in the making.

What do the Banff Springs snail, the Vancouver Island pocket gopher, and Nova Scotia's Blanding turtle have in common? They are species that live in Canada and they are close to extinction. Now, these little guys and 230 other species can breathe a little easier. In June 2002, the House of Commons passed Bill C-5, the Species at Risk Act. This law now prohibits the harming or killing of any endangered species on federal land or water. "Critical habitats" are also protected from destruction. A scientific advisory board will decide which species will go on the endangered list, although Ottawa will still have the right to overturn the board's decisions. This could lead to the kind of political interference that environmentalists fear most.

This Act was a long time coming. Two earlier bills died before being passed by Parliament, and this one faced opposition from a wide variety of sources including: the Canadian Alliance, New Democrats, Bloc Quebecois, the Conservative Party, and even some Liberal backbenchers. Environmentalists say the Act is far from perfect but it is a big step in the right direction. Only threatened life forms on federal land and waters are protected, that leaves two thirds of the species at risk in Canada outside the scope of the Act.

Environment Minister David Anderson was only able to give his own bill qualified praise. "Don't expect it to save every endangered species," he said. "But, I trunk this is going to be a major improvement."