Habitat Makes the Difference

Why the loss of habitat in the Big Cypress Swamp is causing problems for the plants and animals that live there - by Kris Thoemke

"We went down the slough afoot just as the thousands of birds in the rookery were awakening. The birds mostly represented by several species of ibis, and were present by the hundreds and thousands on the large cypress trees. In fact, they were so crowded on some of the giant cypress trees that they were continually falling off for want of sufficient room to stand."

It's hard to imagine this scene in the Big Cypress Swamp but these are the words John Kunkel Small used to describe the bird rookery he encountered 68 years ago. One of the earliest naturalists to explore the Big Cypress and record his journey, Small provides us with a written account of the swamp which he describes as "a preliminary survey [that] deeply impressed upon us the wonderful natural history of the little-known region."

What Small and his party saw back then is vastly different than what we see today. The habitat of the Big Cypress changed over the last 68 years. The huge flock of birds Small described as being so loud that they could be heard "for a distance of a mile" are no where to be found.

While some change is normal in natural systems, the rapid changes of the Big Cypress's flora and fauna are largely the result of human influence. If Small were alive today he would tell you that habitat loss was the reason for the change. And, he'd add an epitaph - "I knew it would happen."

Habitat loss is one of the most often sighted explanations scientists use when they talk about why a species declines or becomes threatened or endangered. Without getting too bogged down in ecological theory, there are certain principles of ecology that apply to every species on this planet. One of them is that every organism has certain habitat requirements and that there are limits as to the number of individuals of a species that can survive in a discrete area.

Picture a grass-green pasture with 10 healthy horses in it. Imagine that you've been driving by it every day for a year and never noticed any changes. In nature we would describe this habitat as stable.

Now, imagine that same scene but this time you drive by the pasture one day and discover that a tractor plowed up a fourth of the grass. For the first few days after the loss of this habitat nothing seemed to change. Gradually, however, you began to notice the ribs starting to show on three of the horses. A month later the field only had seven horses in it. The three missing horses were moved to another pasture you were told.

The loss of the grass, which is a habitat loss, resulted in the pasture only being able to support seven horses rather than 10. In this case, the three horses that moved were lucky. they had a place to go where they could survive. When the habitat shrinks in a natural area, the species that weaken usually don't move to another area, they die. If the habitat keeps physically shrinking, it's easy to see how a species could begin to decline and eventually become threatened or even endangered.

While the Big Cypress has lost some of its size in the last 68 years, it hasn't actually gotten that small to justify the decline of the bird populations or even the Florida panther. There are other ways for the habitat to effectively shrink without physically becoming smaller and that is what happened to the Big Cypress.

Back at the pasture, life is blissful for those 10 horses until one day when an unpalatable weed sprouts in a corner of the pasture. It started to grow and thrive because the farmer who owns the adjacent pasture recently excavated a small lake on his land. The lake effected the water table and slightly dried up the soil beneath the horse pasture.

These new conditions favored the weed's growth and, over the course of the next year, it gradually displaced the grass the horses preferred to eat. Casual observers didn't notice the change but the farmer knew what was happening. Eventually he had to sell the horses because he no longer had enough grassy pasture to support them.

We didn't dig lakes in the Big Cypress. But over the last 68 years we did build two dams across the swamp in the form of US 41 and Alligator Alley. Those roads changed the flow of water across the land and that resulted in changes to the vegetation. These alterations contributed to the loss of suitable habitat for the birds, the panther, and just as importantly to the food that both species eat.

The Big Cypress of 1995 is not the same swamp it was when John Kunkel Small visited in 1917. The cypress trees are there although the biggest ones were cut down years ago. The profusion of rare plants is now a spattering of threatened and endangered species. The squawks of flocks of birds so large that they could be head a mile away are now seldom heard small clusters.

Small, we can say in retrospect, knew that the Big Cypress wasn't going to remain untouched by man. The rambling concluding sentence of his narrative reveals the truth about the Big Cypress Swamp that we are living today. " Our time was limited and the region was large, but some day, before drainage and other depredations of civilization, not to mention vandalism, have removed the bloom from that still unspoiled garden, we hope to make another and longer visit to the land of the Big Cypress."