A review of Madagascar's derived grasslands: Low palatability following anthropogenic fires may threaten food security

Abstract

Societal Impact StatementThe 26th United Nations Climate Change Conference emphasised the need to modify practices that negatively impact biodiversity and food security in the context of global change. Following Madagascar's drought‐induced famine, our systematic review supports the theory that grasslands of the Malagasy Central Highland that are subjected to human‐lit fires are anthropogenically derived. Furthermore, these overly frequent fires that characterise much of the Malagasy Central Highland grasslands select poorly palatable grasses. Given the reliance on pastoralism as insurance against crop failure in Madagascar, fire‐dependent practices that degrade rangeland emerge as a threat to food security and biodiversity. Education can mitigate against future humanitarian crises.SummaryFood insecurity is greatest in countries where impacts of global change are predicted to be severe. Many, like Madagascar, rely on livestock‐based pastoralism (and consequently palatable rangelands) for insurance against natural disasters and crop failure. It is recognised that derived grasslands can impact climate and biodiversity. Furthermore, the well‐established palatability‐flammability trade‐off predicts that overly‐frequent fires select increasingly unpalatable, fire‐adapted grassland. The drought‐induced Malagasy famine of 2021 highlights the need to identify factors that threaten food security. Given the ubiquitous practice of rangeland preparation through annual, landscape‐scale human‐lit fires, we evaluate whether Malagasy grasslands are derived and then test for fire‐driven selection of increasingly degraded and unpalatable rangelands across Madagascar's largest grassland system, the Malagasy Central Highland (MCH). We conducted a systematic literature review, evaluating for a palatability‐flammability trade‐off, by determining dominant Malagasy grass species, and then applying functional traits, and palatability ratings to these species. Data were extracted using a suite of relevant search terms, and of 1977 studies identified, 145 were directly relevant to the questions posed. Evidence from the review is compelling for much of the Malagasy highland grassland being derived. Furthermore, Malagasy dominant grass species are fire‐adapted with poor forage‐value, suggesting current burning practices negatively impact both biodiversity and pastoralism. Decreasing rangeland palatability caused by human‐lit fires in a society suffering food insecurity emphasises the need to re‐evaluate pastoralist burning practices. Identifying optimal fire frequencies can avert breaching fire‐induced tipping points to rangeland palatability and the humanitarian crises that may follow.