How does farming contribute to climate change?

The relationship between our increasingly volatile climate and our increasingly insecure food production are caught in something of a vicious cycle. The more we warm the climate, the more pressure on our farms and our ecosystems. But farming itself plays no small part in global emissions. Agriculture, forestry, and our changing of the land accounts for nearly 25% of all anthropogenic greenhouse gas emissions. So which aspects of farming are behind this, and what needs to be done to bring down our farming footprint, as well as protect our biodiversity? The head of the Tropical Ecology and Conservation group at the University of Cambridge, David Edwards.

David - I think there are probably three key issues with farming. The first is that it's driving massive land clearance and that's the single biggest driver of the global extinction crisis. Secondly, would be fertiliser overuse. And that is causing major harm to waterways globally and in particular, where large rivers meet the sea, they're driving massive algal blooms, which is causing problems for fisheries. And then lastly, agriculture is the second biggest driver of global climate change after the burning of fossil fuels.

Will - Given that it's such a large emitter, what is being done at the moment to try and minimise the environmental consequences of farming?

David - Given the scale of the problem at present, too little is being done. First thing I think we really have to do is to make use of the farm and that we do have better indeed there are some models of farming systems globally that suggests that we might need a billion hectares of new farmland to meet rising global demand. And that's simply land that we cannot afford. So that really points to us finding ways to intensify farming on the lands, that we do have to attempt to do that in a way that involves sustainable intensification. And it would suggest then that we would be moving away from the concept of reducing yield on farms that we already have in a bid to perhaps make it a bit more wildlife friendly. Fertiliser is going to remain a key component of the agricultural systems for decades to come, but I think something we really need to target is fertiliser and pesticide and herbicide overuse. And that will be through transfer of technologies and education to communities that are perhaps overusing these commodities. And lastly, and an absolute critical thing at a global level, we've really got to start moving away from the consumption of ruminant meat. So in other words, from beef and from lamb. These two kinds of meat are massively land intensive and they produce massive amounts of carbon dioxide. We're talking around 10 to 50 times more land use and more carbon emissions relative to alternative protein sources like chicken, pork or soy and other vegetable-based proteins. So reducing that demand for ruminant meat will really create space for us to grow other types of crops, to use crops in their feed and for human consumption instead. And to make space as well for habitat restorations, which we really need to help us rein in climate change and keep it beneath two degrees C.

Will - People have been saying that whilst there's this rush to phase out our use of cows due to their individual emissions, if you were to put them in a field, say, in the UK, they can subsist wholly off that field. Whereas something like a chicken would need an adjacent field to grow the corn it eats. So is there a need to balance organism emission versus land emission too?

David - I mean, that's a very interesting take. I think you need to look at this from a kind of whole system perspective. Cows rarely, not always, but they rarely in the UK would live solely upon grass all year. Many of them are brought to the barn in the winter. They may eat silage, but you'll find that a lot of that silage will be enriched with things like soy. And the fact is that cows transfer energy through grass and whatever else they're eating into meat far less efficiently than does a chicken. So a chicken really doesn't require much food to create a usable unit of protein, whereas cows do. The other issue of course with ruminants is the way that they digest their food emits a huge amount of methane. And methane is about 80 times more potent to climate change gas than carbon dioxide. So it's not just about land, it's about the kind of emissions that are embodied in the animal itself

Will - In terms of being able to make best use of the land we currently have. Is there anything to be said for the idea of diversifying agriculture within that same space? If we did mix livestock with crops, could they benefit one another?

David - There clearly are potentials from diversifying farmland. I would suggest that we also have to weigh those in terms of how we would produce land. If you're having mixed cropping, can we use this kind of industrialised agricultural equipment? Perhaps we can't. Then how can we actually farm hundreds of millions of hectares of land? I'm taking a slightly more global perspective. I agree that in the UK, largely in our lowland agriculture at least, in our vegetable production et cetera, we're pretty much at maximum potential yield. But throughout most of the world there are massive areas in which we are failing to produce outputs, yields at the level that is possible. And there's a really nice study from a few years ago that was looking at if we attempted to intensify land globally to bridge those yield gaps in unyielding areas through technological transfer and some advances. And they estimate you can reduce future land demand by about 80%. So that really is hundreds of millions of hectares of land that can be saved. They think you can reduce greenhouse gas emissions by 65%. So there are ways for us to bring agricultural yields and land we do have up and ideally in a sustainable way.

Will - What would be your call to arms as it were? What would you want to see happen to both reduce farming emissions and to increase the biodiversity

David - In terms of reducing emissions and in fact reducing the severity of the biodiversity crisis? I think we really have to accept that the day has come that we cannot afford globally to be consuming ruminant meat. As we have done it's such a climate change driving a land use intensive, a deforestation driving commodity, we can really make the space for massive areas of cropping for human consumption and massive areas of land, either being avoided deforestation or being abandoned. Because we no longer require that land and that can recover to meet some of these massive global restoration targets we have as well to help mitigate climate change. So I think that really is the thing we have to focus on and we have to do that urgently if we're to really tackle the crisis we find ourselves in.