Cows centre of 'vicious cycle' of methane and climate change
Thursday 30 March 2017
Scientists at the Royal Botanic Gardens, Kew, Scotland's Rural College (SRUC) and the Senckenberg Biodiversity and Climate Research Centre, Frankfurt have warned of a “vicious cycle” of climate change, cattle diet and rising methane levels.
In a new paper, published this week, researchers from the three institutions detailed a discovery surrounding plants used to feed livestock; essentially, plants growing in warmer conditions are tougher and have lower nutritional value to grazing livestock, which is potentially inhibiting milk and meat yields and raising the amount of methane released by the animals.
When plants are tougher to digest, cattle produce higher amounts of methane (a greenhouse gas with a global warming potential 25 times stronger than that of carbon dioxide). As this release of methane continues to warm the environment, researchers said the warmer conditions will give rise to tougher, harder to digest plants, compounding the increases in methane emissions.
Dr Mark Lee, a research fellow in Natural Capital & Plant Health at the Royal Botanic Gardens, Kew who led the research commented, ”The vicious cycle we are seeing now is that ruminant livestock such as cattle produce methane which warms our planet. This warmer environment alters plants so they are tougher to digest, and so each mouthful spends more time in the animals' stomach, producing more methane, further warming the planet, and the cycle continues. We need to make changes to livestock diets to make them more environmentally sustainable."
There are several reasons why rising temperatures may make plants tougher for grazing livestock to digest. Plants have adaptations to prevent heat damage, they can flower earlier, have thicker leaves or in some cases, tougher plants can invade into new areas replacing more nutritious species - all of which makes grazing more difficult.
The researchers mapped the regions where methane produced by cattle will increase to the greatest extent as the result of reductions in plant nutritional quality. Methane production is generally expected to increase all around the world, with hotspots identified in North America, Central and Eastern Europe, and Asia, where the effects of climate change may be the most severe. Many of these regions are where livestock farming is growing most rapidly. For example, meat production has increased annually by around 3.4% across Asia, compared with a more modest 1% increase across Europe.
Dr Lee said, "Now is the time to act, because the demand for meat-rich diets is increasing around the world. Our research has shown that cultivating more nutritious plants may help us to combat the challenges of warmer temperatures. We are undertaking work at Kew to identify the native forage plants that are associated with high meat and milk production and less methane, attempting to increase their presence on the grazing landscape. We are also developing our models to identify regions where livestock are going to be exposed to reductions in forage quality with greater precision. It is going to be important to put plans in place to help those countries exposed to the most severe challenges from climate change to adapt to a changing world.”
Global meat production has increased rapidly in recent years to meet demand, from 71 million tonnes in 1961 to 318 million tonnes in 2014, a 78% increase in 53 years, according to statistics from the UN’s Food and Agriculture Organisation, released last year. Grazing lands have expanded to support this production, particularly across Asia and South America, and now cover 35 million km2; 30% of the Earth's ice-free surface.