The spiny desert
In Madagascar's hot, dry south grows the most unusual dry-land flora on Earth, a botanical world with more than 95% of its plants found nowhere else.
The biome at a glance
Life at the extreme
The spiny desert occupies Madagascar's southern tip, the driest, hottest part of the island. The flora it has produced is unlike anywhere else on the planet. Its dominant families, the Didiereaceae, endemic sections of Euphorbiaceae, and Burseraceae, have been solving the problem of survival with almost no water for millions of years.
These are not variants of familiar desert plants. They are the product of a separate evolutionary journey, under conditions more extreme than most of the world's deserts, and much of what they have become has never been studied.
The Didiereaceae: cacti that aren't cacti
The Didiereaceae family, its members Alluaudia, Didierea and Decaryia, grows nowhere else on Earth. They look and behave like cacti, tall, spiny, water-storing, but they are not related to them at all. They arrived at the same solutions to drought entirely independently.
Biologists call this convergent evolution: the same answer reached by different routes. It is one of the clearest living examples anywhere, and it is only visible because this flora evolved in isolation.
Plants that look like cacti but share no ancestry with them, the same problem solved twice, on an island that has been apart for tens of millions of years.
Breathing at night
Many spiny-desert plants use a way of photosynthesising called CAM. Instead of opening their pores in the heat of the day and losing precious water, they open them at night, take in carbon dioxide when it is cool, and use it the next day with their pores shut tight. It is one of nature's most water-efficient strategies, and here it operates under some of the harshest heat any plant faces.
Fragile, and worth protecting
This is a delicate landscape. Its thin soils and slow-growing plants recover poorly from clearance and charcoal-cutting, and the pressure on it is real. Documenting the spiny desert now, understanding what grows there and where, is part of keeping it.
Very few of Madagascar's endemic plants have ever had their genome read, and the spiny desert is among the least studied of all. Almost every species here is a first look at something science has never described in full.