Under future climate change, the northern reaches of the planet will become more suitable for farming, which could help us to feed a growing global population in decades to come. But, researchers warn, as agriculture inches into these new lands, it also threatens to release vast amounts of carbon dioxide from the soil – potentially upending the climate progress we’ve achieved by that point.

This new discovery, led by the University of Guelph and published in PLOS One, showed that an area of the planet equivalent in size to 30% of currently cultivated land could become suitable to agriculture, under future warming scenarios. This huge swathe of land – which the researchers call ‘frontier soils’ – could, if cultivated, release up to 177 gigatons of carbon dioxide. For a sense of scale, that’s more than the amount the United States has released over the course of a century.

The researchers identified the new agricultural frontiers by combining 17 climate models, and looking at 12 major crops to assess the climate suitability of each region to those foods. This revealed that the lion’s share of these new lands would be concentrated in Russia and Canada, regions that are currently unsuitable for farming a wide selection of crops.

But as global temperatures potentially increase in decades to come, crops like wheat, potatoes, and maize will become increasingly suited to these climes. And if that brings more farmers to these regions, the gradual stripping and tilling of land would slowly eke out carbon that’s currently locked into the soil. “Release of carbon from high latitude soils due to warming is already of major concern,” the researchers write. “But [that] may be small, relative to the amounts of carbon that might be released if these areas come under cultivation.”

In fact, if in years to come, agriculture expands into all the available lands identified in the study, there’d be little chance of meeting the Paris Agreement target to limit temperature increases to 1.5 ̊ C.

Yet, emissions aren’t the only potential downside of a northward-creeping agricultural frontier. The new territory would also intersect with 56% of land designated as global biodiversity hotspots, the analysis showed, as well as 22% of endemic bird areas. And, assuming that future farming continues in the same vein, with the widespread application of fertilizers, insecticides and pesticides, that would bring a threat to regional water quality, as well: the researchers estimate that watersheds that provide for almost 2 billion people could become polluted under this future scenario.

By 2050, many projections show, we’ll need to produce 70% more food to feed the planet’s growing population. So the opportunistic advance of agriculture into these fresh new lands might seem like a logical step: if done properly, it could drastically reduce food insecurity and poverty.

But having mapped out the scale of potential impact, the researchers make an appeal that we consider what we’ve got to lose – and whether more production is truly worth the risk. As they explain, humans don’t exactly have a great track record when it comes to land-use: we have a history of unnecessary expansion into landscapes of huge ecological importance, only to realise the enormous environmental ramifications of that decision, later on.

And, right now, the northward encroachment of agriculture isn’t such a distant prospect, the researchers warn: governments in Russia and Canada have already started to promote the settlement and agricultural development of northern lands. Plus, our increasing technological and scientific prowess – which has given us more resilient and productive crops, and precision agriculture, among other things – is making it increasingly feasible to farm in inhospitable conditions.

But just because we can do it, doesn’t necessarily mean we should, the researchers caution. “There are serious negative environmental impacts associated with the unfettered development of climate-driven agricultural frontiers.”