[Preprint] Applications of the Azolla fern in mitigating the impact of climate change on Sub–Saharan agriculture

Global warming increasingly threatens agricultural productivity and freshwater resources across the planet. The accelerated desertification of Sub–Saharan Africa displays a particularly dramatic example of contemporary climate change. Home to more than 300 million people, the Sahel region is confronted with rising temperatures and ecological degradation amid persistent socioeconomic instability and rapidly growing populations. Azolla, a fast–growing aquatic fern, offers a multifaceted biological solution to many of the challenges associated with the environmental change of Sub–Saharan Africa. A large body of research highlights the agricultural versatility of the Azolla genus. Its rapid biomass production, its unique symbiosis with cyanobacteria, and its ability to thrive on wastewater make this plant genus a highly promising candidate for scalable climate adaptation technologies. In this work we introduce the Azolla Vertical Overflow Reactor (AVOR), a fully automated, solar powered bioreactor, designed to continuously generate Azolla–based aquicultural products under Sahelian weather conditions. This carbon negative machine generates its own energy through photovoltaic and photosynthetic operation, whereby a semi–aquatic bioreactor synthesises CO₂ and N₂ into biomatter, purifying water as a byproduct. Drawing on comparative evidence across the genus, we identify Azolla pinnata as the most suitable species for cultivation in the Sahel. with the highest biomass and crude protein yields. This perspective highlights the potential of Azolla based cultivation systems to strengthen food security, promote sustainable biomass production, and enhance ecological resilience in agriculturally marginal regions facing the increasing impacts of climate change.