Climate change isn’t only driven by belching smokestacks. It’s also affected by farmers who use nitrogen-based fertilisers and the lumber industry’s tree-cutting, and it’s putting the world’s food supply at risk.
Land used for activities including agriculture and lumber accounted for about 13% of carbon dioxide, 44% of methane and 82% of nitrous oxide that made its way into the atmosphere between 2007 and 2016, according to the Intergovernmental Panel on Climate Change. They are all greenhouse gases contributing to climate change, the group said in a report Thursday.
The result: Decreasing crop yields that can lead to a scarcity of food, more land being turned into deserts and less plant diversity, according to the report. It argues that less food waste and changes in diet can mean less need to convert land from its natural state, helping to hold off climate change.
“There are many ecosystems throughout the world where we are already seeing the impacts of climate change and land use change, and it emphasises the need for urgent action,” said Jo House, one of the authors of the report and a professor at the University of Bristol, in a conference call with reporters.
The report, prepared by more than 100 scientists, is one of series coming from the United Nations group aimed at driving global discussions on climate change.
There is a chance to take action, the authors said. Cutting down or eliminating the consumption of meat, which would reduce the need to clear land for large cattle ranches, and eating more grains and vegetables will help.
“Diets that are rich in plant-based foods have lower greenhouse gas emissions than diets that are heavy in red meat consumption,’’ said Cynthia Rosenzweig, an author and a researcher at the NASA Goddard Institute for Space Studies in New York. Replanting devastated forests will also help.
Since pre-industrial times, temperatures over land have increased twice as fast as the global average and are higher by about 1.53 degrees Celsius (2.8 Fahrenheit), said Louis Verchot, a researcher at the International Center for Tropical Agriculture in Cali, Colombia, and a lead chapter author for the report.
While plants can have short-term benefits from increased carbon dioxide in the air, those gains won’t last, Rosenzweig said.
In a high-carbon atmosphere, wheat will become less nutritious, losing 6 to 13% of its protein, 4 to 7% of its zinc and 5 to 8% of its iron, the report said. “Now we are finding decreases in nutritional quality in crops,” Rosenzweig said.
Asia and Africa, parts of which already are dependent on imported food, may be the first victims, increasingly vulnerable to intensifying drought as temperatures rise. In lower altitude regions, yields for crops such as wheat and corn are already declining, according to the report, while some animals are growing at slower rates due in part to heat stress.
Rosenzweig said this summer’s heat wave in Europe has already shown how crop yields can fall.
The Bloomberg Agriculture Spot Index, a price measure of nine crops, plunged to the lowest in a decade in May as global grain supplies were set to swell. But the index in June surged to a one-year high as too-wet weather in the U.S. and hot conditions in Europe stoked worries that harvests would shrink instead. The volatile moves in prices show how quickly food prices can rise amid adverse weather.
Already, large parts of the Amazon rain forest are being lost in Colombia, Peru and Brazil, Verchot said. Melting of the permafrost in Arctic areas will also lead to more greenhouse gases escaping into the atmosphere, as will a massive shift by South American farmers to use more nitrogen fertilizers.
The Earth has been able to absorb carbon, “but that subsidy could very easily be lost if we continue on current trajectories, if we continue to have the land degradation, the ecosystem degradation, the soil degradation, and the water degradation we’re currently experiencing,’’ Verchot said.
© 2019 Bloomberg L.P.