The environmental consequences of climate-driven agricultural frontiers

Discussion This paper has three specific implications as well as raising some broader scale issues that need to be reflected on. In terms of the specific implications, we note that while climate change is cre- ating new opportunities for agriculture, especially in northern latitudes, results presented here show huge potential environmental trade-offs. The first potential impact relates to the release of soil organic carbon into the atmosphere. As shown in the results section of this paper, if agricul- ture is allowed to extend into all of the frontiers identified here, then there would be little chance of reaching the Paris climate accord’s goals of keeping climate change to within 1.5˚C above preindustrial levels [60]. A second implication relates to biodiversity. The results of this paper suggest that if all of the frontiers are converted into agricultural uses, the world will lose important biodiversity hotspots in both mountainous and northern regions. This will accentu- ate the negative impact of what some scholars describe as “the Anthropocene” [61]. This paper shows that a third implication of developing all of these agricultural frontiers would be signifi- cant problems of water degradation that could affect the health and well-being of millions of people. With that said, it is important to acknowledge that the analysis presented here does not assess economic incentives and constraints on frontier development, nor does it simulate the probability that individual areas would be cultivated. Consequently, the carbon, water and bio-

diversity impacts described here are all “upper bound” estimates and in some ways represent worst case scenarios. However, the magnitude of impacts identified, and the potential for very significant feedbacks in terms of environmental problems (such as cultivating the Northern frontier leading to increased carbon emissions leading to more rapid climate change), should trigger concern. In this way, the results presented here should be seen alongside literature on biogeophysical “tipping cascades” that could push the Earth System across a planetary thresh- old to a ‘Hothouse Earth’ pathway [61]. We have identified climate-driven agricultural fron- tiers as a coupled natural-human tipping cascade that might have similar self-reinforcing tendencies. In lieu of more detailed analyses, there are several reasons to believe that frontier development, particularly in the Northern Hemisphere high latitude frontiers, is of both global and regional policy significance. Standing aside from these ecological issues, these results also have implications for society and mean that this analysis makes a contribution to the broad area of sustainability science and the emerging literature on planetary boundaries and planetary health [62–63]. In parti- cular, there are serious social issues that would need to be considered that fall outside of the scope of this paper. A great many First Nations communities call these areas home and have ancestral claims many of which are unseeded. The development of any agricultural “frontier”

would, therefore, need to be done fully cognizant of the fact that Indigenous Communities must be at the forefront of any development plans and must be the primary beneficiaries. Any such developments, therefore, must take into account a number of the following. First, humanity has a history of cultivating land that was once deemed unlikely to ever justify cultivation–and this has created massive sustainability problems. For example, a combination of policies and technology created conditions that led to the Dust Bowl of the 1930s in North America [64]; or that 60 years ago resulted in the beginning of the degradation of the Aral Sea and the pollution of its waters, with knock-on effects on the very same ability of lands to sustain agricultural productivity [65]. Similarly, 50 years ago, no one seriously thought that people would ever turn large areas of the Brazilian Cerrado and Amazon into soy fields or large areas of Southeast Asian peat into oil palm plantation. In particular, the fragile tropical soils were deemed unsuitable and the areas were considered too remote. Yet land use conversion hap- pened in a very short period of time driven by rising demand and low land prices. Arguing by The environmental consequences of climate-driven agricultural frontiers PLOS ONE | https://doi.org/10.1371/journal.pone.0228305 February 12, 2020 11 / 19