Wetlands overview: unique and super important habitats

This post serves to give basic information on wetlands so that in future posts I will be able to build on this knowledge as I don’t want to assume what my readers do and do not know. In the simplest terms, a wetland is a place where plants grow in soil that is soaked with water including; swamps, bogs, marshes, and mangroves. Wetlands are often small and surrounded by other biomes. Wetlands have the 2nd highest species diversity of terrestrial ecosystems, after tropical rainforests. Some of the largest wetlands worldwide are the Huson Bay Lowlands, Everglades, Okavango Delta, Nile Delta, Sundarbans, and the Pantanal. Ironically, wetlands in the past had been viewed very negatively, therefore, they were often drained for farmland. Today we recognize the value of wetlands especially when it comes to soil filtration and storm protection. Wetland delineation is becoming more common as a part of environmental assessments in which soil and plants are measured to try and reduce the number of wetlands disturbed, later posts will focus on this process.


My personal favorite wetland, photo credit: Uncle Pete, Inlet, NY


Some wetlands are seasonal and only occur when there are huge amounts of rainfall. Bogs are a type of wetland that relies almost entirely on rain as their source of water. rainwater also tends to be acidic and poor in nutrients. The result of this is that bogs are fairly infertile and plant growth takes a very long time. Bogs are associated with colder regions and sphagnum moss. Because bogs are such a poor environment to live in they develop layers and layers of undecomposed plant material which becomes what we call peat. As it can hold lots of water and energy-rich it is used for gardening and as a heat source. Over millions of years, peat can become coal as well. A great way to remember that bogs are an unproductive environment is to remember that in Siberia we have found wooly mammoths (Mammuthus primigenius) so well preserved we might be able to clone them. The same would not be true if the mammoth died in a productive ecosystem as it would have been recycled back into the system. Carnivorous plants are also common in bogs as they don’t have to rely on nutrients for the soil. The most common types include sundews (Drosera), pitcher plants, a Venus fly -traps (Dionaea muscipula). Thanks to increased demand for them as houseplants Venus fly-traps are facing population declines although removing a wild plant is now a felony.


Sundews, Photo Credit: Uncle Pete, Inlet, NY


Some wetlands are part of a natural fire regime, like Okefenokee Swamp in South Georgia. This helps to maintain populations of shrubs and smaller trees otherwise hardwood species would take over the swamp and make it a poor habitat for the species that currently live there. Some species of plants even depend on fire to signal them to reproduce.These fires are able to burn due to a large amount of organic material found in them. A fire also directly releases minerals in the form of ash, simulates an increase in primary productivity, reduces competition amount plants, increases the number of food herbivores, and reduces the number of plant pathogens in the environment.

Plants in wetlands have a variety of adaptions as the soil is waterlogged. Often this provides poor support for larger plants to grow, so tree like the bald cypress (Taxodium distichum) have developed buttresses and tree knees. Many plants also have aerenchyma which are special pore holes that allow oxygen to enter the plants and be transported to the roots. Other plants have hollow stems that facilitate this transportation as well, and woody plants are able to pump oxygen from their stems to the roots. Coastal wetlands plants have further adaptions to deal with the salinity of the water. Waterlogged soil is also oxygen-poor. In dry soil, the void space is typically filled with air, and therefore oxygen. This is not the case in wetlands. This is what also gives them the classic swamp smell. Bacteria in soil typically use cellular respiration to produce energy but that requires oxygen so wetland bacteria break down plant material and produce sulfur and methane in the process.


Bald cypress (Taxodium distichum), captured by Lauren Schramm, Okefenokee National Wildlife Refuge. 


The Pantanal is probably one of the most fascinating wetlands, it is the largest tropical wetlands and it is located in Brazil, Paraguay, and Bolivia and about the size of Washington state. During the rainy season, as much as 80 percent of the land is underwater. Here the apple snail (Pomacea bridgesii), is actually a keystone species as it feasts on plants that are submerged, and then die. When the plants die they start to consume all the oxygen in the water. Because the snail has both lungs and gills it is able to breathe air, which it does through a snorkel-like tube. Other decomposers in the environment die but the apple snail is able to recycle the plants for the next year. The Pantanal is also home to the giant river otter (Pteronura brasiliensis), which can be over 6 feet long, and to the largest and healthiest remaining population of jaguars (Panthera onca). In 1996 it was determined that the Pantanal is home to over 10 million caimans, making it the highest concentration of crocodilians in the World. The wetlands serve as a nursery for young animals and an important stopover location of migrating birds.


The giant river otter (Pteronura brasiliensis) is a fierce predator and will even eat caiman.


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