NEWS
Tree planting schemes can destroy rangelands and damage pastoral livelihoods
Ian Schoones
Next time you sign up for a ‘ carbon offset ’ scheme that promises to plant trees somewhere in the world to mitigate the effects on the climate , make sure you check the small print .
In the build-up to COP26 later this year , tree planting is all the rage and huge targets are being set . In 2011 the
United Nations ’ Bonn Challenge proposed that 350 million hectares of land would be ‘ restored ’ through tree planting by 2030 . National governments and regional blocs too have massive plans for more trees , including notorious projects such as the Sahelian ‘ Great Green Wall ’. The AFR100 initiative , funded by multiple international donors including the World Bank , has committed to afforesting 100 million hectares in Africa over the coming decade .
Restoration myths
But is this always a good idea ? Not necessarily . Many of the areas earmarked for tree planting are rangelands . Estimates vary but many millions of hectares of rangelands have been identified by the
World Resources Institute based in Washington DC and the
Crowther Lab at ETH Zurich for forest ‘ restoration ’. This assumes that these are ‘ degraded ’ forests in need of rehabilitation , rather than highly productive , biodiverse ecosystems that support many livestock and people , and according to
Joseph Veldman and colleagues such global restoration assessments may massively overestimate the climate mitigation of tree planting schemes .
and colleagues show , 40 % of the WRI map – some 1 billion hectares – was focused on grassy biomes , highlighting an ‘
inconvenient reality ’ for large-scale restoration plans . As
Catherine Parr and colleagues argue , tropical grassy biomes remain poorly understood and are under threat . In particular , ‘ restoration ’ through tree planting in such areas would have major negative consequences for wildlife , biodiversity and pastoral livelihoods .
Grassland ecosystems and carbon dynamics
Forest Landscape Restoration Initiative – result from a basic misunderstanding of rangeland ecosystems that exist across more than half the world ’ s surface . This is simply ‘ bad science ’. Rangelands are what Bond calls ‘ open ecosystems ’, variegated mixes of trees and grasslands existing together in savannahs and parklands . These are maintained by grazing , fire and human actions , and are some of the most biodiverse areas on the planet . Carlos Martorell , an ecologist from UNAM in Mexico , explains this in a short film , presented at a recent IYRP ( International Year for Rangelands and Pastoralism ) event .
As Carlos explains , grasslands may also fix carbon more effectively than forests , although estimates vary wildly . In the geological past , the expansion of grasslands may have locked up so much carbon it resulted in a cooling of the atmosphere , precipitating an ice age . Grasslands have extensive root systems and high turnover with dead vegetation matter regularly incorporated into the soil , often assisted by grazers . Grasslands can be more reflective of solar ra-
In a 2019 paper , called ‘
the trouble with trees ’, William Bond and colleagues showed how the areas identified for tree planting overlap with grassy biomes ( including rangelands ), wildlife species richness and livestock production ( see figure 2 ). In fact , as
Veldman
23 Grassroots Vol 21 No 3 November 2021