The Irrigation Burden
I find the assumption that robusta provides a climate-resilient solution for sustaining global coffee production to be incorrect. The literature review published Aug. 27 in Sustainable Development by Aaron Davis, Akshay Dashrath, and Justin Moat states "climate resiliency claims for farmed robusta are misguided." These researchers argue that major robusta-producing regions in Vietnam, Brazil, and India lack the natural conditions for rain-fed coffee. In northern Espirito Santo, Brazil, the most important robusta-producing state, 90% of the crop relies on irrigation. This reliance on irrigation and low tree-shade cover, as well as high synthetic fertilizer use, works against "aspirations for ecosystem and biodiversity stewardship" and "goals for a low carbon economy." Because robusta accounts for 43% of the global coffee trade and Brazil and Vietnam together provide 65% of robusta exports, these intensive practices create environmental pressure. Davis has previously researched coffee species beyond arabica and robusta as production faces threats from climate change and a lack of genetic diversity. The research, funded by the Calleva Foundation and the Amar-Franses Foster-Jenkins Trust in the UK, suggests that much more detailed climate mapping will be needed to identify where rain-fed robusta can sustainably expand.
The Water Requirement
The review examined over a century of research and added a new analysis of water availability around wild robusta populations in Africa. Wild robusta evolved in warm parts of tropical Africa where soil water is generally available through rainfall, rivers, wetlands, groundwater, or high water tables. Climate-suitability models based mainly on temperature and rainfall can mistake irrigated farms or naturally wet sites for evidence that robusta can thrive under drier conditions, even though wild populations rely on rivers or high water tables. The authors write, "We contest that this proposition is not supported by scientific evidence," regarding the idea that current cultivation provides a straightforward way to sustain production. Davis and his colleagues suggest expanding production in places that match the plant’s natural water and temperature requirements rather than abandoning the species. Kew researchers previously established liberica and excelsa as genetically distinct species and proposed the name Coffea x libex for hybrids between liberica and excelsa.
