Eating less meat and squeezing more produce out of the land are ways in which we can mitigate climate change and tackle the food crisis simultaneously. In order to investigate the impact that these changes might have on biodiversity, Tom Powell and Tim Lenton, both from the UK’s University of Exeter, modelled four different scenarios that we might follow: high-meat diet and low agricultural efficiency; high-meat diet and high agricultural efficiency; low-meat diet and low agricultural efficiency; and low-meat diet and high agricultural efficiency. They studied the impact that each of these scenarios had on land use change, climate change and biodiversity.

As expected, the high-meat, low-efficiency scenario led to the worst outcome. “In this scenario we found that by 2050 much of the temperate and tropical forests will have been converted to pasture or fodder crops, leaving little but desert and boreal forest, which to us spells a clear ecological disaster,” said Powell. The model findings, published in Environmental Research Letters (ERL), showed that biodiversity would drop by around 20% for both farmland and natural biomes. Meanwhile, the low-meat, low-efficiency scenario was little better. “In this case the prevalence of low-intensity grazing means that the relatively slight reduction in per capita consumption of animal products doesn't have a huge impact,” Powell said. And in both cases carbon-dioxide and global temperatures would continue to soar.

For the high-efficiency scenarios the model assumed considerable changes in farming practices would be put in place, including intensive livestock rearing systems, more fodder crops, higher grazing intensities and recycling of agricultural and food waste. Any land freed up by this increased agricultural efficiency was then assumed to be available to grow bioenergy crops, thereby helping to mitigate climate change. In both of the high-efficiency scenarios Powell and Lenton saw an overall contraction of the land required to support farming for food by 2050, and an easing of global temperature rise, which at first glance seems like good news. However, super-efficient fields and the rise of bioenergy crops are bad news for biodiversity.

“When we intensify farming, especially in the cases in which we replace pasture with high-yielding biomass crops, we are extracting a greater proportion of the available ecological energy from the habitat, leaving very little for any other organisms,” Powell told environmentalresearchweb. “If we are removing upwards of 60 or 70% of the biomass, and especially removing much of the residue (straw etc.) from the fields, what is left is not far removed from a desert from the perspective of other organisms.” And all of this is before the impact of pesticides and fertilizers has been considered, which would likely crush biodiversity further.

The low-meat, high-efficiency scenario had the most positive outcome in terms of tackling climate change, because significant areas of land are freed up for bioenergy crops. But the conversion of pasture to bioenergy crops meant it was still a disaster for ecosystems, resulting in a near 40% drop in biodiversity on farmland, their results showed.

Either way the model suggests the outlook is not good for biodiversity. If we fail to tackle global warming then climate change will take its toll but if we tackle climate change then our super-efficient farms will wipe out wildlife. That said, it isn’t all doom and gloom. There are less destructive ways of improving agricultural efficiency, such as biochar production, minimizing food wastage, recycling manure and sewage, and hi-tech fertilizer-application systems (with precise timing and delivery, for example). “I think what is really important is that we focus on the fact that farming is not only about increasing yields year on year, but is also about managing a swathe of ecological processes,” said Powell.

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