Declining populations of baobab trees have been a concern for more than a decade now. That concern has been amplified with the release of a recent study that shows that two baobab tree species endemic to Madagascar risk losing the majority of their available habitat due to climate change and human development in the coming decades.
Baobab trees are spectacular sights. Unique in appearance, they can grow up to about 100 feet tall with trunk diameters as wide as 36 feet and can live for hundreds (possibly thousands) of years. As the trees age, they develop hollow trunks used for storing water (as much as 26,000 gallons!) to help them survive long periods of drought. The fruits of baobab trees are coconut-sized and edible and are said to taste like sherbet. The leaves of at least one species are eaten as a vegetable, and the seeds of some species are used to make vegetable oil. Various other products, including fibers, dyes, and fuel are also derived from baobab trees.
There are nine species of baobab trees (Adansonia spp.). Eight are native to Africa and one is native to Australia. Two of the African species are also found on the Arabian Peninsula, and six of the African species are found only on Madagascar. Three of the Madagascan species (A. grandidieri, A. perrieri, and A. suarezensis) are listed as endangered on the IUCN Red List. Currently, A. perrieri has the lowest population of the three species, with only 99 observed trees. It is estimated that by 2080, its range will be reduced to 30% of what it currently is, further threatening its survival. A. suarezensis has a considerably larger population (15,000 trees) but a much smaller distribution area (1,200 square kilometers). By 2050, this area is estimated to be reduced to only 17 square kilometers, practically guaranteeing its eventual extinction. On the bright side, A. grandidieri has a population of about one million trees and an extensive range that should remain largely undisturbed in the coming decades.
An interesting component to this story is how giant tortoises fit in. The fruits and seeds of baobab trees are relatively large, and so their dispersal is best carried out by animals. Seeds that fall too close to the parent trees have little chance of survival since they will be shaded out and will have to compete with large, adjacent trees. Animals that eat the fruits of the baobab trees help to disperse the seeds by defecating them in areas away from large trees where the seedlings will have a greater chance of survival. Two species of giant tortoises that were once native to Madagascar but have now been extinct for hundreds of years were likely primary dispersers of baobab tree seeds. A recent study used a species of giant tortoise not native to Madagascar (the Aldabra giant tortoise) to test this hypothesis. The tortoise readily consume the fruit of the baobab tree. The seeds remain in the tortoise’s digestive system for up to 23 days, giving the tortoise plenty of time to move to an area suitable for seed germination. Given these findings, biologists are currently working to introduce Aldabra giant tortoises to Madagascar to help save the baobab trees.
Climate change, loss of habitat due to human development, and loss of seed dispersers due to extinction threaten the survival of some baobab tree species, but by recognizing this threat, biologists can work towards preventing their eventual extinction. As we gain a better understanding and appreciation for the need for biodiversity on our planet, we will resolve to take greater steps to protect it.
To learn more about baobab trees facing extinction and giant tortoises as seed dispersers, visit the Scientific American blog, Extinction Countdown, here and here.
photo credit: wikimedia commons
I was curious if you ever thought of changing the page
layout of your site? Its very well written; I love what youve got to say.
But maybe you could a little more in the way of content so people could
connect with it better. Youve got an awful lot of text
for only having one or 2 pictures. Maybe you could space it out better?
Thanks for the feedback. I try to keep my posts short (less than a thousand words) so that they are quick reads and not too text heavy. I agree that the blog could be more visually appealing. I will try to include more photos to break up the text. Thanks for reading!
Here’s a vote for more text just to complicate things for you. 🙂 I love photos but I get frustrated by articles that are image heavy but light on words. Anyway, I came here in search for more information on Baobab trees and learned some things so this article was definitely useful and well written. I was wondering if you, awkwardbotany, know anything about the animals and birds who live in or frequent African Baobabs. My husband and I had a poicephalus rufiventris (Red Bellied Poicephalus) parrot as a pet and they were said to live in Baobabs in Senegal but I’ve been unable to find much if any information about them in the wild. Thank you for any information- and thank you for the lovely site!
Thanks for the input. I actually think I have done a little of both in recent posts – a few more photos and a bit more text. I try to post at least once a week, so longer posts are challenging. The most important thing to me is that the information be useful and interesting. I really don’t know much about the animals and birds that use baobab trees. I wish I did though. I’m not even sure where to start. I like browsing through Encyclopedia of Life (www.eol.org). Also, searching for Adansonia on the IUCN Red List might yield something (http://www.iucnredlist.org/search). They have lots of links for references and resources associated with each entry.
Thanks very much for reading! I am happy to hear you are enjoying the blog.
Thank you for the ideas for more research. I do love to learn new things. I can understand longer posts being problematic especially if you’re posting once a week. Since your posts are exactly what you want- useful and interesting- I’m not sure you need to change things much at all. Thanks for writing.