January 15, 2013

Ten Thousand Islands, Everglades National Park, Florida

The Ten Thousand Islands are vast area of mangrove forests consisting of islands and sloughs along the western-side of South Florida from Florida Bay to the Gulf Coast. This is one area of the Everglades that many people overlook or do not know about. But, it is a shame because it is a fascinating area of incredible ecological significance. One thing to be aware of is that this corner has one of the highest mosquito densities on the entire planet in summer, with up to 2 billion per square mile. So, definitely come in winter when it is cooler, drier, and without the constant assault of flying hyperdermic needles.

The other nice thing about visiting this unknown corner of Everglades National Park, is that it is away from the massive crowds and urban jungle of Miami and the main road of the national park. The Ten Thousand Islands area is anchored by the Gulf Coast Visitor Center in the tiny town of Everglades City, Florida. There are only two or three hotels in the town, so plan early. From the visitor center, you can book a concessionaire boat trip to explore the mangrove swamps and see amazing wildlife.

Mangroves are unique among plants in their ability to survive not only submerged in water, but in saltwater. There are three species of mangroves in these forests. Red mangroves are the ones most tolerant of saltwater and are the early successional species. These small trees have air-roots that grip the brackish mud and hold onto it. This allows a growth of the land and the next species to take hold, black mangroves. In addition, there is a rarer third mangrove called the white mangrove that grows back in the stand above the standing water. One other tree commonly seen on these mangrove islands are the buttonwoods.

These mangrove islands are in tidal zones. While the tides are relatively small in this region, only fluctuating 2-3 feet per tide. But, because the water is so shallow in these areas, it has a significant impact on the movement of water in the sloughs and across the islands. During low tides, these islands can be high-and-dry. But, when the tide rises, there is standing water across almost all of these islands.

For wildlife, that means having to deal with being wet and salty multiple times per day and without much solid surface to hold onto. For the Colusa Indians who inhabited these mangrove swamps, it was a difficult living, despite the abundant food sources. But, they did have a strategy to given themselves some dry land to sleep on. On some of these islands, they would pile up the massive quantities of discarded oyster shells from their meals to literally make dry islands they could place their villages on.

Ancient Colusa oyster shell midden

Mangroves are incredibly important ecosystems, despite their relative paucity of terrestrial species. The dense tangle of prop-roots creates sancturaries for juvenile fish to develop without the risk of open water predators. Many of the most important large marine fish species begin their lives as tiny larva hiding out in the mangroves before they are large enough to hold their own in deeper waters. The presence of these dense thickets allows for the accumulation of sediments and thus the building of new land.

Roseate spoonbills feeding in the mud of the mangroves

One of the most important aspects of the mangrove forests for the millions of people who live in South Florida are their ability to control the power of hurricanes and tropical storms. Their presence, as a wall against storm surges, absorbs the energy of these surges and prevents them from advancing as far inland, protecting homes, lives, and property. They also reduce the amount of open water that fuels hurricanes, allowing the strength of the storm to be diminished before heading further inland.

The ospreys are back after they almost went extinct due to DDT in the '60s.

The abundance of wildlife in these shallow waters and dense thickets is astounding. The mangrove cuckoo is only found in these forested areas and no where else on Earth. The presence of ibis, wood storks, green-backed herons, blue herons, tri-colored herons, snowy egrets, and many other wading birds makes a boat trip through this area a bird-watchers paradise.

So, if you do find yourself in South Florida on a warm, dry winters day, take a trip over to Everglades City and book a tour to visit the mangroves. You will not be disappointed.

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