Climate change and the thermal performance of a high protein food source: Wolffia globosa

Wolffia globosa is a tropical duckweed native to Southeast Asia, where it is harvested for food. This aquatic plant has a fast growth rate, a high protein content, and is also a source of important nutrients. Therefore, it could play an important role in food security under climate change and population growth. We provide the first thermal performance curve for W. globosa, and use this data to understand how climate change impacts on temperature in Southeast Asia may affect production. We find that the maximum relative growth rate occurs at constant temperatures of [~]32C. We find no significant difference between growth at current mean conditions and temperatures predicted in the next 40 years according to the high emissions scenario (SSP5-8.5 scenario) in Thailand, Laos and Myanmar when temperatures are held constant. However, the thermal performance curve is best described as asymmetric, with growth rates that fall rapidly at temperatures above this optimum. As a result, when temperatures are allowed to fluctuate about the mean in a pattern similar to recent heatwave conditions in Thailand, we find significantly lower growth rates at the optimum than at current mean temperatures. This decrease is driven by a significant increase in frond death at higher temperatures. However, given the fast growth rate of this species relative to other food crops, and the mitigating impact of water on the magnitude of temperature fluctuations, it seems likely that W. globosa may more rapidly recover from extreme heat events than other crop species. Therefore, it is likely to be a suitable candidate for adapting to climate change impacts.