Reforesting pasture land to offset UK CO2 emissions

Among the more interesting posters exhibited at the LEAP 2019 Conference in Oxford was one submitted by Drs Helen Harwatt and Matthew Hayek of the Harvard Law School.  The poster summarised the findings of their April 2019 report Eating Away at Climate Change with Negative Emissions.  Subtitled Repurposing UK agricultural land to meet climate goals, the report examined two scenarios in which UK agricultural land currently devoted to livestock rearing, both directly as pasture and indirectly as land used to grow animal feed, would be wholly (scenario 1) or partially (scenario 2) reforested in order to offset the UK’s carbon dioxide (CO₂) emissions.

Under the Climate Change Act, the UK is legally bound to reduce greenhouse gas (GHG) emissions by 80% compared with 1990 levels by the year 2050, and the government has recently upped this to set a net zero emissions target by 2050.  Limiting global warming to 1.5 degrees Celsius (1.5℃), in line with the Paris Agreement, would demand even more rapid reductions in GHG emissions.  However, the UK is not currently on track to meet even the 80% reduction target.

In addition to a massive reduction in GHG emissions, tackling the problem will require carbon dioxide removal (CDR) from the atmosphere, and the most readily deployable CDR option in the UK is the restoration of its native forests.  Animal agriculture currently occupies almost half (48%) of UK land, whether as pasture (~84,000 km²) or for growing feed (55% of the ~58,000 km² of cropland).  The authors found that under scenario 2, in which land currently used for growing feed would be converted to diversified fruit and vegetable production for human consumption, thereby increasing UK food self-sufficiency (by value, less the half of the food consumed in the UK is home-produced), reforestation of pasture land would provide a CDR of 3,236 million tonnes CO₂, equivalent to 9 years of current UK CO₂ emissions.  Scenario 1, in which all of the land currently devoted to livestock rearing would be reforested, would provide a CDR of 4,472 million tonnes CO₂, equivalent to 12 years of current UK CO₂ emissions.  In relation to the 1.5℃ global warming limit, CDR at these levels would extend the UK’s permissible GHG emissions budget to 2050 by 103% and 75% under scenarios 1 and 2, respectively.

Although neither scenario is likely to be realised, at least in the short term, the report demonstrates the massive potential that the reforestation of land currently used for rearing animals provides for offsetting UK GHG emissions.  As the authors of the report conclude: “Restoring agricultural land currently used for farmed animals back to native forest would contribute substantially to aligning UK GHGs with the Paris Agreement, and provide new opportunities for alternative protein production, fruit and vegetable provisions, and enhanced food security … providing additional benefits including habitats for the reintroduction of wildlife.”  This is surely preferable to the National Farmers Union’s optimistic and largely unproven hi-tech plan for UK agriculture to become carbon neutral by 2040 by growing biofuels for power stations and then capturing and burying the carbon dioxide, increasing the carbon stored in soils, and using technology to reduce the emissions caused by cattle and fertiliser.

Paul Appleby