Globally human populations are growing, trade is increasing, and living standards are rising for many. But, according to the UN's latest Global Environment Outlook report, long-term problems including climate change, pollution, access to clean water, and the threat of mass extinctions are being met with "a remarkable lack of urgency".

Over the last 20 years, the human population has increased by a third, global trade has tripled, and per capita income has gone up by 40%. Annual emissions of the main greenhouse gas, carbon dioxide, have also increased by one third.

As the human population grows it has reached the point, the UN says, "where the amount of resources needed to sustain it exceeds what is available".

Sixteen thousand species are threatened with extinction. Habitat loss is a major factor as many forests are cleared for agriculture. The UN estimates the global annual loss of primary forest is 50,000 km2.

The availability of fresh water will decline, according to the UN, who project that by 2025 1..8bn people will be affected by water scarcity. Sanitation is also a major issue, as contaminated water is the greatest single cause of human disease and death.. The state of the world's fisheries is also touched on by the report which says many fish stocks are overexploited, while the demand for fish is expected to rise alongside growing populations.

By the end of 2007 it is estimated that more people will live in cities than rural areas for the first time in history. The satellite image of the US city of Las Vegas (left) shows how rapidly metropolitan areas can grow. The city was home to 557,000 people in 1985, by 2004 this had risen to nearly 1.7 million. This rapid growth can put pressure on water resources and infrastructure.