Large-scale crop plantations are expanding at a rapid pace across southeast Asia, with multinational firms often benefiting the most at the expense of local communities and the environment, two U.N. rights experts warned on Wednesday.

Demand for agrofuels, such as those derived from sugar cane and palm oil, has boomed thanks in part to the United States, Europe and other rich economies seeking alternative ways to fuel their cars and homes in order to reduce their carbon emissions.

Tough new limits on the maximum sulphur content of shipping fuels will come into effect in Europe at the end of the decade, after EU governments agreed on draft legislation on Wednesday.

Air pollution from marine fuels with a high sulphur content is estimated to cause 50,000 premature deaths a year in Europe, the European Parliament has said.

"This is excellent news for our health and the environment, especially in ports and coastal areas," EU Environment Commissioner Janez Potocnik said in a statement.

The mystery surrounding the deaths of at least 877 dolphins in Peru deepened on Wednesday as the government said human activity was not to blame but failed to pinpoint a natural cause for the massive die-off.

A final report from the Peruvian government's Ocean Institute, which manages one of the world's richest marine ecosystems, said the dolphins did not die from a lack of food, hunting by fishermen, poison from pesticides, heavy metal contamination, an infection or a virus.

Killer heat fueled by climate change could cause an additional 150,000 deaths this century in the biggest U.S. cities if no steps are taken to curb carbon emissions and improve emergency services, according to a new report.

The three cities with the highest projected heat death tolls are Louisville, with an estimated 19,000 heat-related fatalities by 2099; Detroit, with 17,900, and Cleveland, with 16,600, the Natural Resources Defense Council found in its analysis of peer-reviewed data, released on Wednesday.

A yearly review of countries' greenhouse gas emissions cut pledges under an extension to the global climate pact the Kyoto Protocol could be a way to raise climate ambitions, the European Union's lead climate negotiator said on Wednesday.

Negotiators from over 180 countries are meeting in Bonn, Germany, until Friday to work towards getting a new global climate pact signed by 2015 and to ensure ambitious emissions cuts are made after the Kyoto Protocol expires at the end of this year.

Indonesia's progress in reforming its forestry sector will not be sufficient to meet its pledge to reduce carbon emissions by 26 percent by 2020, Norway's environment minister said on Tuesday.

Indonesia imposed a two-year moratorium on clearing forest last May under a $1 billion climate deal with Norway aimed at reducing emissions from deforestation, despite resistance from some government departments and from resource firms looking to expand in the archipelago.

A row over planning how to bind all emitters under a global climate pact from 2020 at U.N. climate talks in Germany is blocking negotiations to deepen nearer term emission cuts and raise cash to help poor countries cope with a warming planet, the EU said Tuesday.

Delegates have failed to start work on a new Durban Platform negotiation track after four days of talks in Bonn spent arguing over an agenda to organize work this year and appoint a chair to steer the process.

Reluctance to raise ambitions to cut greenhouse gas emissions due to economic constraints is threatening progress towards limiting global warming, delegates at United Nations' climate talks in Germany warned on Monday.

The talks in Bonn, which end on May 25, are partly to discuss ways of raising the level of ambition on cuts but the worsening eurozone crisis and battered global economy have increased reluctance to commit to more financially onerous cuts by the end of the decade, delegates told Reuters.

Indonesia's government said on Monday it would protect a strip of peatland in Aceh province at the centre of an international storm over palm oil development, in a case that had become a test of the country's commitment to halt deforestation.

Indonesia imposed a two-year moratorium on clearing forest last May under a $1 billion climate deal with Norway aimed at reducing emissions from deforestation, but the former governor of the country's westernmost Aceh province breached the ban by issuing a permit to a palm oil firm to develop the peatland.

Coastal seagrass can store more heat-trapping carbon per square mile (kilmometre) than forests can, which means these coastal plants could be part of the solution to climate change, scientists said in a new study.

Even though seagrasses occupy less than 0.2 percent of the world's oceans, they can hold up to 83,000 metric tons of carbon per square kilometer, a global team of researchers reported Sunday in the journal Nature Geoscience.

That is more than twice the 30,000 metric tons of carbon per square kilometer a typical terrestrial forest can store.