Policymakers are not adequately factoring land use and human diets into climate mitigation strategies – “The fundamental problem is that policymakers and researchers have not truly confronted the fact that global land area is limited”
4 January 2019 (Mongabay) – A recent study finds that governments and researchers routinely underestimate the potential for changes to land use and human diets to reduce greenhouse gas emissions and mitigate the impacts of global warming.
Published in Nature last month, the research suggests that policymakers are not adequately accounting for the amount of carbon that could be stored in forests and other natural vegetation if those lands weren’t used for producing food, and are also failing to recognize the carbon emissions that will result from increased agricultural production.
According to the study’s lead author, Tim Searchinger, a research scholar at Princeton University and a senior fellow at the World Resources Institute, these oversights on the part of climate policymakers are particularly crucial because successfully mitigating climate change will require more carbon to be stored in forests and other vegetation, even while the world will have to produce as much as 50 percent more food every year in order to feed the growing global population.
“We have to take the implications of policies for land use even more seriously than people have been doing,” Searchinger said in a statement.
“The fundamental problem is that policymakers and researchers have not truly confronted the fact that global land area is limited. Using any hectare (2.47 acres) for one purpose comes at the cost of not using it for another, and these opportunity costs have not been truly accounted for. The need is to make more efficient uses of land for all purposes.” [more]
ABSTRACT: Land-use changes are critical for climate policy because native vegetation and soils store abundant carbon and their losses from agricultural expansion, together with emissions from agricultural production, contribute about 20 to 25 per cent of greenhouse gas emissions1,2. Most climate strategies require maintaining or increasing land-based carbon3 while meeting food demands, which are expected to grow by more than 50 per cent by 20501,2,3,,2,4. A finite global land area implies that fulfilling these strategies requires increasing global land-use efficiency of both storing carbon and producing food. Yet measuring the efficiency of land-use changes from the perspective of greenhouse gas emissions is challenging, particularly when land outputs change, for example, from one food to another or from food to carbon storage in forests. Intuitively, if a hectare of land produces maize well and forest poorly, maize should be the more efficient use of land, and vice versa. However, quantifying this difference and the yields at which the balance changes requires a common metric that factors in different outputs, emissions from different agricultural inputs (such as fertilizer) and the different productive potentials of land due to physical factors such as rainfall or soils. Here we propose a carbon benefits index that measures how changes in the output types, output quantities and production processes of a hectare of land contribute to the global capacity to store carbon and to reduce total greenhouse gas emissions. This index does not evaluate biodiversity or other ecosystem values, which must be analysed separately. We apply the index to a range of land-use and consumption choices relevant to climate policy, such as reforesting pastures, biofuel production and diet changes. We find that these choices can have much greater implications for the climate than previously understood because standard methods for evaluating the effects of land use4,5,6,7,8,9,10,11 on greenhouse gas emissions systematically underestimate the opportunity of land to store carbon if it is not used for agriculture.
Assessing the efficiency of changes in land use for mitigating climate change
