Human Demographic Outcomes of a Restored Agro-Ecological Balance

As prominent features of the Anthropocene, biodiversity loss and invasive species are exacting serious negative economic, environmental and societal impacts. While the monetary aspects of species invasion are reasonably well assessed, their human and social livelihood outcomes often remain obscure. Here, we empirically demonstrate the (long-term) human demographic consequences of the 1970s invasion of a debilitating pest affecting cassava -a carbohydrate-rich food staple-across sub-Saharan Africa. Successive pest attack in 18 African nations inflicted an 18 {+/-} 29% drop in crop yield, with cascading effects on birth rate (-6%), adult mortality (+4%) and decelerating population growth. The 1981 deliberate release of the parasitic wasp Anagyrus lopezi permanently restored food security and enabled parallel recovery of multiple demographic indices. This analysis draws attention to the societal repercussions of ecological disruptions in subsistence farming systems, providing lessons for efforts to meet rising human dietary needs while safeguarding agro-ecological functionality and resilience during times of global environmental change.