In 1966, Florida ecologists covered mangrove islands with giant tents and fumigated every insect, then watched life rebuild from nothing

In 1966, two American scientists asked a bold question. If every single animal on a small island vanished overnight, would life find its way back? And would the island end up looking the same as before?

To find out, ecologist Edward O. Wilson and his graduate student Daniel Simberloff picked seven tiny mangrove islands scattered across Florida Bay, near the Florida Keys. According to Wilson and Simberloff's 1969 study in the journal Ecology, they wrapped each island in a large tent and pumped in a fumigant called methyl bromide, killing off nearly every insect and spider living there while leaving the mangrove trees themselves untouched.

Why Florida's mangrove islands were the perfect lab
These weren't random islands. According to the same 1969 study titled ‘Experimental Zoogeography of Islands: Defaunation and Monitoring Techniques,’ red mangrove islands in Florida Bay are small and simple, made up of nothing but mangrove trees rising straight out of the water, with no soil or undergrowth to hide in. Each island measured only about 35 to 60 feet across, small enough that researchers could locate and identify almost every creature living on it before the experiment even began. The islands typically held between 20 and 50 arthropod species at any given time.


That gave Wilson and Simberloff a rare opportunity in ecology: a true before-and-after picture of an entire animal community, followed by a chance to watch what recolonized the islands.

What happened when the tents came down
When the fumigation was over, nobody knew what to expect. Some feared the islands would sit empty for years. Others speculated that whatever came back would be a random, chaotic mixture that looked nothing like the original community.

However, within weeks, insects and spiders started to arrive, drifting in on wind currents, rafting in on floating debris, or flying in from nearby islands, according to Simberloff and Wilson's companion 1969 study. The same study found that most of the islands had similar species numbers and composition as before the fumigation, within about eight months or 250 days. The exception was the island furthest from any other land, which lagged behind. The researchers called this the first direct experimental evidence of what ecologists call faunistic equilibrium: the idea that an island naturally fell into an equilibrium between arriving species and species dying out.

A finding that still shapes how America protects its wild spaces
Here's why a 1966 experiment still matters to anyone living in the US today. The same balancing act that took place on those mangrove islands is true for any patch of habitat surrounded by something hostile to wildlife, be it ocean water or a highway.

As cities and farmland continue to cut forests into smaller, more isolated patches, national parks, wildlife refuges, and even suburban green spaces are increasingly acting like islands. According to a widely cited 2008 review by ecologist William Laurance, published in the journal Biological Conservation, island biogeography theory remains a foundational framework for understanding how fragmented habitats lose species over time, even as later research has added nuance around edge effects and the surrounding landscape. The same review, ‘Theory meets reality: How habitat fragmentation research has transcended island biogeographic theory,’ also points out that the theory has shaped decades of thinking about the importance of reserve size and connectivity in conservation planning.

Part of the reason is that conservation groups in the US usually push for larger protected areas that are connected, rather than small ones that are isolated, and why wildlife corridors that connect separate habitat patches have become a higher priority in recent decades. The other part the reasoning goes back to those fumigated mangrove islands in Florida Bay.

The bigger lesson about nature's resilience
Besides the influence on conservation planning, there’s something reassuring about what Wilson and Simberloff discovered nearly 60 years ago. They didn't just test a theory. They showed that an ecosystem that has been wiped out has an inherent tendency to re-establish itself, given time and a nearby source of newcomers.

That doesn't mean that every damaged ecosystem recovers this easily. The mangrove islands were small and close to much adjacent habitat, so recolonization was quicker than it might be for a badly fragmented mainland forest far from any intact wilderness. But this basic pattern of life bouncing back and settling into a new balance, recorded by the two scientists, is repeated again and again in ecology.

Almost six decades later, the mangrove island experiment is still taught in ecology classrooms across the country, not as some strange footnote from the 1960s but as one of the clearest demonstrations that nature, even when stripped bare, knows how to start over.