Conservationists generally disapprove of flooding species-rich habitats.

But the law of unintended consequences works in mysterious ways.

For it was just such a flood, in 1913, that created Barro Colorado Island in central Panama.

Gatun, the lake surrounding the island, was, at the time of its birth, the largest artificial body of water in the world. It formed the middle passage of the Panama Canal.

Barro Colorado, meanwhile, has become the most intensively scrutinised scrap of tropical rainforest on Earth.

The field station from which this scrutiny is conducted opened in 1924, and in 1946 it was taken over by the Smithsonian Institution, which dubbed the operation the Smithsonian Tropical Research Institute (STRI).

Since then, the island, and some neighbouring areas of forest on the mainland that have fallen under the STRI's auspices, have turned into biology's equivalent of a big physics facility like CERN, the home of the Large Hadron Collider.

Though the STRI itself employs only 35 scientists, a further 1,200 visit each year, many of whom are regulars.

To mark the field station's centenary, a horde of old hands and enthusiastic youngsters gathered on June 18th in Gamboa, the island's nearest town, for three days of festivities to celebrate the past and plot the future.

They discussed everything from how new species arise and the effect of lightning on insect ecology, to tropical forests' role in curbing climate change.

Biology's hundred-year scrutiny of Barro Colorado means its wildlife has been recorded in exquisite detail.

The current roll lists 110 species of mammal (70% of which are bats), 384 birds, 33 frogs and toads, two salamanders, 23 lizards, 41 snakes, more than 400 ants, some 600 butterflies, 10,000 beetles and even 100 cockroaches. There are also 1,400 species of plants.

Given this abundance, it is hardly surprising that the place has been the source of several fundamental ecological findings, and many new techniques of observation.

Early on, for example, it provided the first good test of the idea that the number of species a patch of habitat can support depends on its area.

The so-called species-area relationship predicted that Barro Colorado's sudden isolation would cause local extinctions. Which it did.

Ornithologists saw bird species dwindle in number by more than a quarter, while remaining unchanged in similar habitats on the mainland.

Among other things, that result demonstrates the value of scale, if nature reserves are to be effective.

Barro Colorado also hosted the first serious study of wild primates (howler monkeys, by Clarence Ray Carpenter in the 1930s), the first big field investigation of echolocation in bats (by Donald Griffin in the 1950s),

and the first attempt to attach numbers to the obvious truth that the tropics support more species of creepy-crawly than temperate climes do.

This was launched in 1971, by Terry Erwin, an entomologist who "fogged" tree canopies on the island with insecticide, collected what fell out, and recorded the arthropods he found in each tree type.

Combining this information with estimates of the number of tree species around the world, he concluded that Earth supported about 30 million sorts of insects and other terrestrial arthropods.

The current calculation is about a quarter of this, so it was not a bad estimate. The island's plants have not been neglected.

Between 1981 and 1983 a block of 50 of its 1,560 hectares was surveyed in detail by Robin Foster and Stephen Hubbell, to record the location and species of every tree and shrub with a stem-diameter of more than 1 centimetre (initially, these numbered 242,000).

The Forest Dynamics Plot, as it is known, has since been resurveyed every five years, permitting the life cycles of many woody plants to be understood in far better detail than was previously possible.

It has also inspired the establishment of 77 similar plots in forests around the world, both tropical and temperate, containing 7 million specimens of 13,000 species.

On top of all this, the STRIhas itself provided a salutary example of the social evolution of American science over the past century.

The field station's founders were men carved in the image of Theodore Roosevelt, the American president whose methods for getting the Panama Canal built included involving his country in a minor war.

(The old-boy culture endured, as sexual-misconduct allegations revealed in 2021 made plain.)

Today, though, the institute has become—fittingly—more representative of human diversity.

It is one thing to measure and describe the luxuriant biodiversity of the tropics, though, and quite another to explain it. Speciation's details can be hard to demonstrate.