The environmental problems faced by the world are so extensive that they must be treated as a top priority if they are to be solved, scientists have told the United Nations.

A team of 400 researchers involved in putting together the fourth Global Environment Outlook: Environment for development (GEO4) said that the “scale of the challenge is huge”.

They assessed a range of environmental factors and concluded that the condition of the land, sea, air and rivers have all deteriorated in the past 20 years.

Achim Steiner, executive director of the United Nations Environment Programme (UNEP), said that the international community’s response to environmental issues was at times “courageous and inspiring”, but all too often was inadequate.

“The systematic destruction of the Earth’s natural and nature-based resources has reached a point where the economic viability of economies is being challenged and where the bill we hand to our children may prove impossible to pay,” he said.

The report was critical of the lack of action by governments across the world in protecting the environment from being degraded. The response to climate change was described as “woefully inadequate” but it was only one of several major problems that needed to be addressed effectively.

“We appear to be living in an era in which the severity of environmental problems is increasing faster than our policy responses,” the report said. “To avoid the threat of catastrophic consequences, we need new policy approaches to change the direction and magnitude of drivers of environmental change.”

Mike Childs, of the environmental campaign group Friends of the Earth, said: “The steady degradation of the world’s environment threatens the wellbeing of everybody on the planet.”

John Sauven, the executive director of Greenpeace UK, said the report illustrated the importance of living sustainably. He said: “It is the only way to improve global life expectancy and income inequality, beat climate change, reduce deforestation and protect biodiversity.”

Population

Increases in world population, which has risen almost 34 per cent from 5 billion in 1987 to 6.7 billion today, were blamed for many of the pressures on the Earth’s resources.

Consumption, heightened by a threefold increase in trade since 1987, means that more is now being produced than can be sustained, especially as average incomes have increased 40 per cent per person since 1987. Each person needs 21.9 hectares of the Earth’s surface to supply his or her needs whereas, it was calculated, the Earth’s biological capacity is 15.7 hectares per person.

Atmosphere

Developed nations were found to have made significant achievements in cleaning up air pollution but the problem has intensified in many poorer nations.

Changes in policy and legislation coupled with improvements in technology reduced air pollution in some cities but was negated in other places because of increased economic activity and a growth in the use of cars.

Richer countries were, the report said, responsible in some cases for shifting their pollution to developing countries that were producing goods for export.

Climate change was regarded by the report as “visible and unequivocal” and likely to have enormous impacts on the environment. Combating it should be treated as “a global priority”, it said.

Researchers, in line with warnings from the UN International Panel on Climate Change, said drastic steps were required by policymakers to reduce greenhouse gas emissions from energy, transport and land use. “Fundamental changes in social and economic structures, including lifestyle changes, are crucial if rapid progress is to be achieved,” the report said.

Land

The output of an average farmer increased 40 per cent since 1987 as land use intensified to keep up with the growth of the global economy and population.

Each person in the world was said, on average, to require a third more land to supply individual needs than the biological capacity of the landscape. “Unsustainable land use is causing degradation, a threat as serious as climate change and biodiversity loss,” the scientists concluded.

“It affects human wellbeing, through pollution, soil erosion, nutrient depletion, water scarcity, salinity and disruption of biological cycles.”

Of particular concern to the researchers was the increase in fertilisers required to meet demands for food because of the contamination the chemicals can cause.

Irrigation was said to be reducing the quantity and quality of water in rivers. One in ten of the world’s main rivers now runs dry at some point each year before it can reach the sea.

Genetically modified crops were regarded by the scientists as essential if food demands are to be met because they can protect against disease and pests. Insects were said to destroy 14 per cent of all crops. Rising desertification and droughts were feared to be destroying soil quality.

Water

Overfishing was singled out as an issue that needed to be tackled as a priority or else billions of people could face food shortages in the coming decades.

“Marine fish catches are being maintained only by fishing ever further offshore and at deeper levels, devastating some species very quickly, and increasingly further down the food chain,” the authors said.

It was pointed out that 60 per cent of the world population live within 65 miles of the coast and that many are likely to be forced to move because of sea level rises from global warming over the coming century.

Availability of fresh water was high-lighted as a rising problem. By 2025 1.8 billion people were forecast to be suffering from severe shortages.

Biodiversity

Measures to protect biodiversity, with species being forced into extinction at a rate 100 times faster than any in fossil records, were regarded as urgent.

The rate of loss was considered so serious that it was described as the sixth major extinction event in the Earth’s history.

“Human life and all other species depend on healthy ecosystems. But current biodiversity changes, the fastest in human history, mean losses are restricting future development options,” the report said.

About 60 per cent of ecosystems were described as degraded or used unsustainably, with land-use change, habitat loss, overexploitation and pollution all factors. Introductions of alien species were blamed for widespread damage to habitat.

“Reducing the rate of loss and ensuring that decision-makers acknowledge biodiversity’s full value to human wellbeing will go far towards achieving sustainable development,” the authors said.

The researchers said agriculture depended on biodiversity but was the biggest cause of reduced genetic diversity, species loss and habitat loss. Scientists expressed concern for the future security of the supply of food because of the narrow genetic base for agriculture. “Just 14 animal species account for 90 per cent of all livestock production, and 30 crops dominate global agriculture, providing an estimated 90 per cent of the world’s calories,” they said.

Concern about diversity extended to human cultures. More than half the world’s 6,000 languages are under threat and some estimates put the likely loss this century at 90 per cent.

“Increased understanding of how people relate to biodiversity and how to move towards greater stewardship of biodiversity may be the biggest question the world must still answer,” they said.

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