Ecosystem Ed.: Wetlands

Back in January, I wrote a post about how we tend to pay more attention to animals than we do to habitats, and why that can sometimes be problematic. Then I managed to do exactly what I warned readers not to do for the next 8 months: focus on the animals and not the habitat. So in an effort to draw attention back to the environments where these animals live, I’m starting a series of posts that focus on different types of ecosystems around the world! In each of these posts (which will be sprinkled in periodically with others), I’ll break down each type of ecosystem to the basics: what, where, why, how, and who, along with some fun facts.

Image by Tsilia Yotova.

First, just a quick reminder of what an ecosystem is: a community of living things and nonliving natural components that exist together and interact with each other. An ecosystem can be as big as a giant coral reef, or as small as a single rotting log on a forest floor. There are several categories of ecosystems on Earth, ranging from rainforests to deserts to grasslands. This week, we’re focusing on WETLANDS.  


What is a wetland?

Bond Swamp National Wildlife Refuge, Georgia, USA. Image by USFWS.

As the name suggests, a wetland is an area of land that’s… well, wet. It’s inundated with water, either seasonally or year-round. Most wetlands are freshwater, although coastal ones can have saltwater mix in to create brackish estuaries. There are a few different types of wetlands, distinguished by the type of plants that are dominant. Swamps are forested, marshes are shrubby, bogs are mossy (and tend to be somewhat acidic), and fens are grassy mires. River flood plains and deltas are also considered wetlands. If you want to get technical about it, the defining characteristic of a wetland is that its water table is high enough for long enough each year to support aquatic plants.


Where can we find them?

Wetlands of all shapes and sizes can be found around the world, on every continent (although the ones in Antarctica and northern Russia and Canada are frozen over). They can form anywhere that receives enough water, whether that be through rain/snow, a nearby river or ocean, or more recently, human intervention (artificial wetlands are sometimes created for wastewater treatment). Some of the more notable ones include the Everglades in Florida, the Okavango Delta in Botswana (made famous by the BBC’s Planet Earth), and the Pantanal in Brazil.

The Okovango Delta floods every year, drawing thousands of animals. All of those dark spidery lines are tracks from where animals passed through the flooded plain. Image by Joachim Huber.


Why do they matter, and how do they work?

This simple science experiment shows just how much plants filter water. Image from Starnet.

Swamps and bogs may not seem very appealing to us, but they do a lot to support the environment. All that soil and plant life acts as a giant sponge, soaking up rain and rivers to prevent flooding. They also serve as a filter, removing pollutants from water that passes through. Without wetlands, flooding and dirty water become a major issue, as certain coastal cities have discovered. With our changing climate, we can expect more extreme weather and more flooding in the future, so wetlands are more important now than ever before. And of course, all those plants usually means more oxygen production and resources for wildlife.

One thing that people often associate with wetlands is the not-so-great smell, which is the result of organic material decomposing. Decomposition can produce a lot of gases, including methane – I have vivid memories of visiting a marsh on a school field trip where the group leader poked a stick into the muck to release some gas, and then set it on fire without warning! I was in middle school at the time, so you can imagine the sheer volume of fart jokes.


Who lives there?

Egret wading in Everglades National Park, Florida. Image from NPS.

Wetlands are FULL of life – they’re some of the most biodiverse ecosystems on the planet. There was a tiny swamp close to my house that I used to bike to every so often – it was full of frogs and salamanders and turtles and crayfish and all kinds of insects, and I occasionally saw herons and eagles in the area. Apparently, there used to be beavers around too, but I never saw any there (probably because some houses were built nearby when I was pretty little). Depending on where in the world you are, you might find different types of amphibians and reptiles, all sorts of fish, crustaceans, wading birds, plant-eating mammals, and sometimes large predators – the Sundarbans mangrove forest in Bangladesh hosts the world’s largest population of wild Bengal tigers, for example.

Of course, the main sort of life you’ll find in wetlands is plant life – all that water can support all kinds of aquatically-inclined plants, a.k.a hydrophytes. Hydrophytes can include plants that grow best when fully submerged, floating plants like lilies, water-loving shrubs, certain trees like mangroves or cypress, mosses, algaes, and grasses and sedges (like cattails). Any wetland plants have to be able to take in a lot of water without drowning, and also tend to have large root systems that can help filter out pollutants.


Fun Facts:

American alligator in Tosohatchee Wildlife Management Area, Florida. Image by Mary Keim.

  • The wetlands of southern Florida (including the Everglades) is the only place in the world where alligators and crocodiles co-exist in the wild! Other crocodilians (also usually found in wetlands) include caimans and gharials.
  • There’s a popular rumor among residents of Washington D.C. that the city was built on swampland (literally – I’m not talking politics here). It’s particularly persistent during D.C.’s hot and sticky summers. However, historical analysis revealed that while there were probably a few patches of wetland here and there, most of the area was pretty well-drained (especially for being between two rivers). That didn’t stop periodical flooding in the early days of the city though.
  • Going by the technical definition of “wetland”, the world’s largest is the Amazon River Basin that covers almost half of South America.
  • Peat bogs, or wetlands that contain very little nutrients and are made up of deposited organic material from dead plants. They tend to be acidic, and plants grow slow and decay occurs even slower. This slow decay means that organic material can be preserved for thousands of years – all sorts of historic/archeological objects have been found in peat bogs across Europe, including wood objects, textiles, and even bodies with hair, organs, and skin intact.
  • Estuaries are areas where ocean water mixes with river water to create sheltered brackish environments, which are crucial for many marine animals' life cycles. I grew up next door to the largest estuary in the US, and one of the largest in the world: the Chesapeake Bay.