Galapagos land habitats are largely determined by their vegetation, and the vegetation is determined by local climate. In turn, local climate reflects aspect and altitude, because most of the rain is generated by rising air, brought by prevailing winds from the southeast.
Because of this, the Galapagos vegetation is strongly zoned by altitude, with four universally recognized vegetation zones:
- the Littoral Zone under the influence of salt spray along the coast
- the Dry Zone, which is the largest vegetation type in Galapagos
- the Transition Zone of dry woodland
- the Humid Zone, of Scalesia forests, Miconia scrub and highland grasslands.
The Littoral and Dry Zones occur on almost all islands throughout the archipelago, while the other zones occur only on the large, high islands, with their verdant, fog-shrouded mountain peaks and slopes. Each zone has its own distinct collection of species. More about the vegetation zones
The world-famous land plants and animals of Galapagos include Darwin’s finches, giant tortoises, land iguanas, tree cacti, and many lesser known but equally important members of the ecosystem, such as more than 60 endemic land snails. Many of these endemic species exist on only one island, or only in certain locations.
Various factors in Galapagos including isolation and small population sizes favor rapid evolutionary changes, allowing closely related populations to follow separate evolutionary tracks leading to speciation and diversification.
The very nature of an archipelago promotes evolutionary change due to the many different degrees of geographical isolation found there: the archipelago is isolated from the continent, the islands from each other by different distances, and the habitat types by their climatic differences.
I never dreamed that islands, about 50 or 60 miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted; but we shall soon see that this is the case. It is the fate of most voyagers, no sooner to discover what is most interesting in any locality, than they are hurried from it; but I ought, perhaps, to be thankful that I obtained sufficient materials to establish this most remarkable fact in the distribution of organic beings.
Darwin, C. (1906). The Voyage of the Beagle. London: New York, J. M. Dent; E. P. Dutton.
While the abundance and distribution of species, or biodiversity, of terrestrial Galapagos is the least altered of any tropical oceanic archipelago, there are currently many challenges to native terrestrial biodiversity.