MEDELLIN (Colombia) • Chicken or beef?

Think carefully: Your choice can help determine the future of the planet.

After raising the alarm last Friday about the fight for survival of many animal and plant species, which they lay at the door of mankind, scientists stressed that we can still redeem ourselves.

And it does not have to be that difficult.

"We do not all have to become vegetarians," said Dr Robert Watson, an atmospheric scientist and head of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), which brought out the first major global species assessment in 13 years.

"But a more balanced diet - less beef, more chicken, more vegetables... can really help relieve the pressure."

The IPBES reports, released at a major environmental conference in Medellin, are meant to guide governments in policymaking. But their authors stressed that we all have a role to play.

When it comes to diet, for example, Dr Mark Rounsevell, a professor of sustainability who co-authored one of the four IPBES reports, pointed out that it takes about 25kg of plant matter to produce 1kg of beef.

Cows are also major emitters of methane, a greenhouse gas that contributes to planet warming, which the IPBES warned is now one of the major threats to biodiversity.

Dr Watson's next tip is "stop food waste".

The clearing of land for farming is a major enemy of biodiversity, driving animals and plants from their habitats.

Yet an estimated 40 per cent of all farmed food goes to waste.

Some changes will require tough choices.

"Get rid of the subsidies in agriculture, transportation and energy that only distort the economic system and lead quite often to unsustainability in a way we manage our biodiversity," said Dr Watson.

Taxes may be needed, and goods might become more expensive.

Today, the "true cost" of producing many goods is not factored into their sale prices, explained Dr Rounsevell.

These include greenhouse gas emissions from raising cows, and the land area required to produce the fodder to feed them.

"Taxes are one way of embedding the costs that are not part of the direct market," said Dr Rounsevell.

AGENCE FRANCE-PRESSE