The environmental consequences of potential agricultural activity on land that will become suitable for crops due to climate-change

The environmental consequences of climate-driven agricultural frontiers

L. Hannah, P. R. Roehrdanz, K. C. KB, E. D. Fraser, C. I. Donatti, L. Saenz, T. M. Wright, R. J. Hijmans, M. Mulligan, A. Berg, A. van Soesbergen

Summarized by Mckenna Dyjak

What data were used?: Climate-driven agricultural frontiers are areas of land that currently do not support the cultivation of crops but will transition into crop-yielding land due to climate change. The frontiers were identified using seventeen global climate-models (mathematical representations of atmosphere, land surface, ocean, and sea ice used to project future climates) for Representative Concentration Pathways 4.5 and 8.5 (RCPs, greenhouse gas concentration trajectory). The climates in which twelve globally important crops (corn, sugar, wheat soy, etc.) can grow were determined by using three modeling methods: Ecocrop (model of crop suitability based on known ranges of optimal temperature and precipitation), Maxent (used in determining species distribution under climate change) and the frequency of daily critical minimum and maximum temperatures provided by the NOAA Earth System Research Laboratory Twentieth Century Reanalysis Version 2. Water quality impacts, soil organic carbon impacts (consequences of the release of organic carbon preserved in soil), as well as biodiversity impacts (variety of life in an ecosystem) were data used in this study to determine the outcome of developing the frontiers. 

Methods: The climate-driven agricultural frontiers were found by aligning the preferred climate of crops with the predicted climate determined by the RCPs. The water quality impact was analyzed by using a hydrological model to determine the fraction of water that would be contaminated by the agriculture on the frontiers. Soil organic carbon impacts were determined by using a global dataset that estimates the amount of soil organic carbon present at the top 100cm (soil can store some of the organic carbon that is cycled throughout the earth). The biodiversity impacts were assessed by compiling biodiversity hotspots, endemic (found only in a certain area) bird areas, and Key Biodiversity Areas and comparing them to the agricultural frontiers to find any overlap.

Results: The climate-driven agricultural frontiers were found to cover 10.3-24.1 million km2 of Earth’s surface; the areas can be seen in Figure 1. The models project that the largest portion of frontiers will be in the boreal regions of the Northern Hemisphere (e.g., places where coniferous trees- like pine trees- thrive) and mountainous areas across the world. In these areas, it was found that potato, corn, and wheat are the crops that will make the biggest contribution to the potential agriculture lands. 

Figure 1. These are the predicted global climate-driven agricultural frontiers for RCP8.5 2060-2080 (scenario of future climate if society does not make efforts to cut greenhouse-gas emissions). The areas in blue are future frontiers that will transition from no current ability to support crops to the ability to support one or more crops. The areas in red are uncultivated areas that will transition to support multiple crops.

The release of carbon from the soils in the agricultural frontiers was predicted to be about 177 gigatons of carbon after 5 years of plowing took place on the untilled land (land not cultivated for crops). There is so much carbon stored in the topsoil layer of these frontiers that the 25-40% estimated release is equivalent to around 30 years of current US carbon emissions. These numbers do not include the release of carbon that will occur in the high-latitude soils due to warming alone. When analyzing the biodiversity impacts it was found that 56% of biodiversity hotspots, 22% of Endemic Bird Areas (EBAs), and 13% of Key Biodiversity Areas (KBAs) intersect with the agricultural frontiers. The fact that suitable climates for species will change with warming as well was taken into account (both crop and species suitability moves upslope). Water quality will be negatively affected by the biocide runoff in these frontiers and will affect 900 million to 1.6 billion people, as well as ecosystem health. 

Why is this study important?: Russia is already discussing using the warming land to their advantage for developing agriculture and it is likely that Canada will as well. This study outlines the detrimental outcomes of cultivating these lands and urges for international policies for sustainable development of the frontiers. Due to climate change and unsustainable farming practices current farmland is becoming unusable. With a predicted increase in need for food due to a growing population, as well as unusable farmland, there will be a push for developing new lands; however, it is important to know the potential risks and how to mitigate them.

The bigger picture: With climate change and population growth occurring side by side it is important to know how to handle them in the worst-case scenarios and what measures will need to be taken to do so. It is also important to note that food insecurity is not usually linked to food production but rather to socio-economic disconnects such as food deserts (neighborhoods without healthy food sources). 

Citation: Hannah L., Roehrdanz P. R., K. C. K. B. , Fraser, E. D. G., Donatti, C. I. , Saenz, L., Wright, T. M., Hijmans, R. J., Mulligan, M., Berg, A., and van Soesbergen, A. (2020) The environmental consequences of climate-driven agricultural frontiers. PLoS ONE 15(2): e0228305.

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