Biology Reference
In-Depth Information
Our results provided some new insights and a number of surprises. First, despite there be-
ing 20,000 species on the IUCN Red List, only 800 species found at 600 sites (some spe-
cies shared the same site) met our criteria. Second, half of the species limited to a single site
turned out to be amphibians. Third, many single-population species were restricted to isol-
ated mountaintops. A botanist on our team, George Schatz, cautioned the vertebrate special-
ists against any euphoric notion that saving the world's rarities might be as easy as saving
some isolated mountaintops where few people live. “Remember,” he warned, “the 250,000
or so vascular plant species have yet to be evaluated for levels of threat. At least 10 percent
of these are known only from the single site where they were first collected.” There is a joke
among field biologists that rarity is partly a natural phenomenon and partly the result of some
less energetic biologists failing to wander far enough from the road or the field station in
surveying their specialty. There may be an ounce of truth to that, but the idea that the popula-
tions of many plant species, and the insect species they host, could be so few only reaffirms
the important role of rarity, especially in the tropics.
The next question for our group of biologists was which rare species or place we should try
to save first. This exercise drew us to a global map and triggered much debate. “Here.” Mike
Parr leaned over northern South America to point out the location of a mother lode of rarities.
His pen tip lingered on a massif that stood by itself in northern Colombia, the Sierra Nevada
de Santa Marta. The solitary giant sat about 42 kilometers from the Caribbean coast and about
115 kilometers from where the sawtooth eruptions of the northern Andean chain began. Santa
Marta in Colombia, like Mounts Kilimanjaro and Udzungwa in Tanzania, Mount Cameroon
on the border of Nigeria and Cameroon, and Mount Kinabalu in Sabah, Malaysia, are but a
few of the dozens of solitary mountains in the tropical belt that are hotbeds of natural rarities.
Why this might be so was one of the questions I wanted to investigate.
“Here is where I want to go next,” I said, pointing to the Zapata Swamp on the island of
Cuba. Considered the Cuban version of the Everglades, this freshwater swamp is home to the
Cuban crocodile, the Zapata wren, the Zapata rail, and two species of hutia (a guinea pig-like
rodent) found nowhere else in Cuba, the Caribbean, or anywhere else. In the same swamp are
the only robust populations of several Cuban birds—the Cuban sparrow, Fernandina's flick-
er, Gundlach's hawk, and the blue-headed quail-dove—proving that rarity is not confined to
tropical mountains or even rain forests.
As we populated the map in front of us and delved into the causes of rarity for the 800
species that met our conditions, we saw another insight into rarity confirmed. Some of these
species had likely always been rare, such as the 13 frog species sharing the same genus and
the same mountaintop in Haiti, the Massif de la Hotte; others on the list had been made rare
by human activities. Some species had been much more common during an era when the cli-
mate was different from what it was during our mapping project—colder, hotter, drier, wet-
ter. They were now climate refugees. Some species had been doing fine at a single site until
