Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain diverted to biofuels.

Increasing energy use, climate change and carbon dioxide emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced.

Using biofuels instead of fossil fuels will do little to cut carbon emissions, and could even increase them because of the extra land the crops will require.

The wildlife trade monitoring network TRAFFIC issued a wake-up call to the Indonesian authorities this week: stop the illegal trade in Sumatran tiger body parts or the species will be hunted to extinction.

Global warming is not a uniform process. Mongolia, particularly at the high altitudes around Lake Hovsgol, has been warming more than twice as fast as the global average. Unique ecosystems are feeling the heat. Here at the transition between the steppe grassland and taiga, plants and animals are confronted with a changing environment-and the outlook is not good for the herders who are crowding up from the south.

"We apologise for recent price increases," reads the sign over the bread counter, "but they are due to global factors beyond our control." This is not a Third World food stall but an upscale supermarket in Brussels, capital of the European Union, whose farming system was once notorious for the mountains of surplus grain it produced. Those mountains are now gone. The world is down to its lowest grain stocks for decades, and food prices are up around the world.

A common assumption is that ecosystem services respond linearly to changes in habitat size. This assumption leads frequently to an "all or none" choice of either preserving coastal habitats or converting them to human use. However, the researchers survey of wave attenuation data from field studies of mangroves, salt marshes, seagrass beds, nearshore coral reefs, and sand dunes reveals that these relationships are rarely linear.

While cutting down rainforests to grow palm oil for biofuels may constitute "madness" (1 December 2007, p 50), burning other vegetable oils is no more sane, nor less damaging to Indonesia's rainforests. Indonesia is expected to increase its palm oil production by more than half over the next 10 years. This is driven, in part, by China, which used to buy rapeseed oil from Europe for food and for industrial uses, but is switching to Indonesian palm oil because Europe's cars and trucks now burn the rapeseed oil as a biofuel.

Many biofuels are associated with lower greenhouse gas emissions but have greater aggregate environmental costs than gasoline.