Australian acacias: Weeds or useful trees?

Abstract

By promoting Australian acacias to the developing world, aid and development agencies are failing to learn from the mistakes made with mesquite (Prosopis juliflora) and jatropha (Jatropha curcas)— two plants with weedy attributes that have done more harm than good when promoted in Africa as aid. The belief in ‘‘miracle’’ plants that can lift people quickly out of poverty is problematical, because such plants have the attributes of weeds—vigorous growth in degraded conditions—and often escape human control, degrading rather than improving land. Other problems are costs that are less obvious than benefits, discounting of the future, and a belief that anything green is good. The main biological problem with Australian acacias is copious crops of long-lived seeds which make eradication very difficult, binding future generations to acacia-dominated landscapes. Drawing on papers presented at a workshop on Australian acacias as introduced species around the world held at Stellenbosch University, I examine the different perceptions of Australian acacias by invasion biologists and the aid and development community. The latter has redefined ‘‘sustainability’’ to give it social rather than ecological goals. To manage Australian acacias sustainably, precautionary risk assessment should take precedence over adaptive management, because mistakes are often irreversible and can take many decades to become obvious.