SINGAPORE - Mankind will have to overhaul the way it grows food if it is to curb the impacts of climate change and to clothe and feed billions more people, a major UN report will say this week.

About a third of the Earth's land area is used for agriculture to feed 7.7 billion people. But booming demand for food and resources has pushed the planet to the brink.

Decades of expansion for farming and forestry has caused widespread land degradation globally. Poor farming practices, especially in drier areas, has led to widespread erosion of soils and loss of biodiversity while huge areas of forest and wetlands have been cleared for palm oil, soy, cattle ranching and rubber.

Climate change is expected to make things worse, scientists say, because extreme weather such as more intense droughts and floods risks greater erosion of soils, compounding the threats already facing farmers and food production.

That is likely to mean millions more people, especially in poorer nations, will struggle to grow enough food, triggering mass migrations.

Scientists and policymakers from around the globe are meeting in Geneva this week to finalise a report that is expected to underscore the crisis facing agriculture and suggest solutions to make farming more sustainable and cut food waste.

Doing so is urgent because agriculture and forestry emit about a quarter of humanity's greenhouse gas emissions. Cutting down forests, draining peatlands and ripping up grasslands emits huge amounts of carbon dioxide (CO2), while rice paddies and cattle ranching produce large amounts of methane, a far more potent greenhouse gas than CO2.

It's a vicious cycle. Destroying nature in this way removes a key tool for humanity to soak up excess emissions that are heating up the planet and fuelling more extreme weather.

Adding to the urgency, humanity has very little time left to make drastic emission cuts from all sources, including transport and power stations, to avoid dangerous climate change, the UN says.

Making agriculture more efficient and greatly reducing its environmental footprint is a key solution in the climate fight, authors of the UN Intergovernmental Panel on Climate Change (IPCC) will say in their special report on land use, due for release on Thursday. It is also vital if the world is going to be able to feed 10 billion by 2050.

A leaked draft of the report said it would be impossible to keep global temperatures at safe levels unless there is also a transformation in the way the world produces food and manages land, The Guardian reported.

"It's not going to be a comfortable report to read if you're a policy-maker. There are lots of challenges ahead," Dr Mark Howden, an IPCC vice-chair and Director of the Climate Change Institute at the Australian National University in Canberra, told The Straits Times.

LAND DEGRADATION

More than 100 scientists from 52 countries have spent about three years researching the links between agriculture, land degradation, desertification, food security and climate change.

The Straits Times spoke to some of the authors prior to the Geneva meeting. While not revealing the exact findings of the report, they underscored the urgency of the crisis that countries, including Singapore, are increasingly focused on.

A major problem is land degradation, where farmlands have been damaged by over-grazing, poor cropping practices and tree clearing, making them vulnerable to erosion by wind and rain. In some areas, deserts have spread, exacerbated by more intense droughts.

"We are losing land annually to new degradation in the drylands and other parts of the landscape and that's as a result of unsustainable land management practices, mostly unsustainable agriculture in terms of cropping and also grazing management," said Dr Annette Cowie, principal research scientist (climate) at the New South Wales Department of Primary Industries.

"This is a systemic problem. It's not the individual landholders wanting to cause degradation," she said, adding that pressure to grow food as a cheaply as possible made it hard for farmers to focus on green practices.

"There's all-round pressure globally to produce everything at the absolute bottom cost."

Poor land management practices mean soils no longer hold sufficient organic matter or soak up CO2, she said. That made farming a major part of the climate problem. But that can change.

"We can turn that around with more sustainable practices that would build soil carbon and take carbon out of the atmosphere," she said.

SOLUTIONS

Dr Howden said farmers were already making changes, small and large.

"Small ones are changing cropping practices and changing breeds. The large ones are moving agricultural systems to different areas, fundamental changes in what we see as farming.

"We have to become better at what we do. We need to become more efficient, we need to be thinking about managing increased variability of our climate, we need all of the tools, including seasonal forecasts, but also finance tools, government policy tools such as drought support."

Cutting food loss and waste was another key area.

About a third of all food produced is either lost during transport and handling or wasted by supermarkets and consumers, the UN Food and Agriculture Organisation says. That represents about 8 per cent of mankind's greenhouse gas emissions.

"We need consumer awareness about food waste and appropriate policies from plants to plates to reduce food waste. We all need to know it takes a lot resources and it causes a lot of environmental problems when you produce food," said IPCC author Dr Prajal Pradhan, researcher at the Potsdam Institute for Climate Impact Research in Germany.

"Whenever we are throwing out food, we are also throwing out embedded resources or embedded environmental impacts caused by growing those foods," he said.

Dr Pradhan and Dr Howden said shifting to healthier, climate-friendly diets, such as cutting out meat where possible, could be part of the solution. Placing a higher value on food is another.

"We've become so efficient in the West in terms of producing food and food is so cheap we no longer really value it and nor do we value the farmers who produce it," Dr Howden said. "And one of the large social changes that need to happen is that we need to reverse that."