Madagascar’s Baobab Trees

Context

A new study has uncovered the origins of baobabs,  the distinctive tall deciduous trees often found on the island of Madagascar.

• The study (‘The rise of baobab trees in Madagascar’) from researchers in the UK, China and Africa was published in Nature. 

Baobab Trees

The trees belong to the genus Adansonia, which comprises eight distinct species. Adansonia digitata found in continental Africa, Adansonia gregorii in Northwestern Australia, and six other species endemic to Madagascar.

• Origin of Lineage: According to DNA studies, the trees first arose in Madagascar 21 million years ago. 
  • Their seeds were later carried on ocean currents to Australia and also to mainland Africa, evolving into distinct species.

• Characteristics: Baobabs are known for their great heights, with some extending up to 50 metres, and exceptionally long lifespans going up to 2,000 years. 
  • In India too, a few baobab trees exist, including one near the Golconda Fort in Andhra Pradesh that is believed to be more than 400 years old.
• Keystone Species:  It is a Keystone Species which provide “essential resources, such as food or shelter, for a guild of animals in return for which the guild of animals provides an essential service, or mobile links, such as pollination or diaspore dispersal.” 
  • The absence of keystone species can have destabilising effects on entire ecosystems, given their centrality to them.
• Significance: In local cultures, the trees are revered because of the multiple uses their parts have, with the fruits and seeds being edible, the seed oil used for cooking and the bark fibre for clothing.
  • They are also called “upside down” trees because their tops resemble an uprooted plant turned upside down. 
  • The baobabs play an important biological role in the conservation of ecosystems of which lemurs, sunbirds and hawk moths are important constituents.

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Findings of the Study

• Risks of Extinction: Three baobab species native to Madagascar are at risk of extinction, as indicated by the IUCN Red List of Threatened Species.
  • According to the IUCN, these include residential and commercial development, livestock farming and ranching, which require clearing land.
  • The remaining three are listed under the Least Concern category, meaning they do not face significant threats. 
  • However, their population is declining indicating that more rigorous conservation strategies are needed. For this, a detailed understanding of the genetics of baobabs is needed.
• Vulnerability Assessment: The study highlighted that climate change will pose “severe threats” leading to its extinction before 2080.”
• • An evaluation of Adansonia suarezensis and Adansonia grandidieri indicated significant recent inbreeding. 
  • This suggests that due to their unique ecological niche and limited genetic diversity, they are likely to exhibit “reduced resilience to ecological perturbations and habitat fragmentation.”