LONDON (AP) — A quarter of the world’s mammal species — from tigers to rhinos — could face extinction within 30 years, and water shortages suffered by millions of humans could get far worse, unless there is firm political action to protect the environment, the United Nations said Wednesday.

In a state-of-the-world report, the UN Environment Programme said the Earth faces more rapid, more dramatic and more devastating environmental change over the next three decades.

“The increasing pace of change and degree of interaction between regions and issues has made it more difficult than ever to look into the future with confidence,” the organisation said in Global Environment Outlook-3.

At a London news conference launching the report, UNEP executive director, Klaus Toepfer, said human development “across more and more areas of the planet is not sustainable. Unless we alter our course, we will be left with very little.”

Released in advance of the UN World Summit on Sustainable Development — to be held August 26 – September 4 in Johannesburg, South Africa — the report is based on contributions from more than 1,000 scientists collaborating with the Nairobi, Kenya-based UN agency.

It assesses environmental changes over the past 30 years and looks ahead to the next three decades — a period the United Nations says will be critical in determining the future of the planet.

The report says the world’s biodiversity is under threat, with 1,130 of the more than 4,000 mammal species and 1,183 of the 10,000 birds regarded as globally threatened — meaning they could become extinct but are not necessarily under immediate threat of extinction.

Among the most critically threatened are the black rhinoceros of Africa, the Siberian tiger and the Amur leopard of Asia, according to the UN’s World Conservation Monitoring Centre.

Much of the threat is man-made, with loss of habitat from industry, mining and farming, and the introduction of non-native species in many parts of the world putting species in danger. Fifteen per cent of the world’s land has been degraded by human activity such as overgrazing, the report says, while half the world’s rivers are seriously depleted or polluted.

The report warns that roads, mining and other infrastructure developments could affect over 70 per cent of the world’s surface in the next 30 years.

In addition, almost one-third of the world’s fish stocks are ranked as depleted, overexploited or recovering as a result of overfishing.

Michael Novacek, provost of science at the American Museum of Natural History, said the UN figures are in line with projections that have been made on the basis of land loss and degradation of the oceans “that as much as 30 per cent of species diversity will be erased by the middle of this century”.

“We have a taste of this in marine ecosystems,” he said, citing devastated coral reefs in Caribbean, loss of fisheries in the Mediterranean, and the “hugely threatened” South China Sea, which feeds so many people.

The UN report notes progress in some areas. Air and water quality have improved in the last 30 years in North America and Europe, and the amount of land protected as national parks and reserves has quadrupled since 1970.

The United Nations also says there could be deep cuts in the emission of greenhouse gases linked to global warming if governments show the will to enforce international agreements such as the 1997 Kyoto Protocol.

Global hunger is falling, and could affect as little as 2.5 per cent of the world’s population by the year 2032 — but 40 per cent of the world’s people suffered serious water shortages by the mid-1990s, and 1.1 billion people still lack access to safe drinking water.

The report’s bad news outweighs the good. Weather-related hazards such as cyclones, droughts and floods appear to be increasing in strength and frequency and are affecting more people, 211 million a year in the 1990s, compared with 147 million a year in the 1980s. Some attribute the increase to global warming.

The United Nations says depletion of the ozone layer has reached record levels, with the ozone hole over Antarctica covering more than 28 million square kilometres (11.2 million square miles) in September 2000.

The report argues that political action to decrease both poverty and over-consumption, reduce poor countries’ debt burden and promote good government could help alleviate the worst environmental problems.

“It is not a doom and gloom report,” Toepfer said. “There is, in the developed countries, quite a lot of successes. These successes are not coming like manna from heaven but are the result of political commitment. Where we have political commitment, we can solve these problems.”

Tony Juniper, director-designate of Friends of the Earth, said the report was a “wake-up call to the world”.

“Time really is running out. The Johannesburg Earth Summit is crucial. It is vital that the world’s most powerful nations show leadership and put people and the planet ahead of national and corporate interests,” he added.

But one dissenting environmentalist branded the UN study as alarmist.

“I disagree with the message it sends,” said Bjorn Lomborg, author of The Sceptical Environmentalist, which questions much of the received wisdom of the environmental movement.

“They may be saying it’s not a doom and gloom report, but there’s a tendency to overplay the negative. It’s not correct to say the poor are getting poorer and the world is getting thirstier.”