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Carbon Sinks in the Everglades

By Ruscena Wiederholt, Ph.D., Quantitative Ecologist; Anteneh Z. Abiy, Ph.D., Hydrogeologist; and Steve Davis, Ph.D., Chief Science Officer; The Everglades Foundation.

Anyone who’s been following Wall Street has witnessed the rising inflation, falling stocks, and growing interest rates like an accounting rollercoaster. With such volatility, it’s only natural to turn to the great outdoors for some solace and stability. But don’t let the tranquility of the picturesque Everglades landscapes fool you; they have a set of stocks with as much change and excitement as the world of finance.

Carbon is a natural stock with a reach from the coastal cities of Florida to the frozen depths of the Arctic ice caps. Keep reading to learn more.

The Paradox of Carbon

Carbon is a high-risk, high-reward type of element; rare yet ubiquitous, essential yet destructive. If you scroll down in the periodic table, before going too far, you’ll find the fickle element of carbon. It’s found in our bodies, wispy blades of grass, sparkling diamonds, and the hardest blade and hammer. It's the key element in oil, gas, and the charcoal for your barbecue. On Earth, carbon is surprisingly not very abundant—it makes up less than 0.025% of Earth's crust. Known as the king of elements, it can form more compounds than all other elements combined. This includes an all too familiar form, carbon dioxide. Although carbon dioxide is necessary for life (plants require it for photosynthesis), the surge of this heat-trapping compound in our atmosphere has caused all the vexations of climate change: rising temperatures, sea level rise, increased droughts, and more severe storms. Fortunately, ecosystems that stockpile carbon, like the Everglades, can help.

Taking Stock in the Everglades

Wetlands are natural carbon sinks and, therefore, excellent banks for carbon. Their soils accumulate and hold tons of this element, more than that found in the atmosphere, plants, and animals combined. In terms of carbon bank brands, there’s a variety of choices, but freshwater wetlands are undoubtedly the biggest. Making up most of the wetland area in the U.S., they hold significant stores of carbon.

The Carbon Cycle in Wetlands

So how do wetlands acquire so much carbon? Instead of trading, carbon changes its form and transforms from one sort to another, moving between the atmosphere, soil, and bodies of water. This endless carbon cycle is natural, and everyone has their procurement part to play. For instance, water-loving wetland plants are efficient machines that capture carbon dioxide from the atmosphere during photosynthesis. They also trap sediment, while wetlands store carbon in the plants and animals they harbor. What makes wetlands’ carbon banking system so unique is their ability to trap and build up carbon in its waterlogged soils.

Source: Board of Water and Soil Resources

The Everglades and Soil

In the Everglades, there are two major soil types, peat and marl, and peat soil is undoubtedly our star trader for carbon. In wetland soils, the constant flooding slows down decomposition by microbes, allowing dead and partially decomposed plant and animal matter to accumulate over time. This is particularly true for peat soils, which are rich in organic carbon and other nutrients. The Everglades, though, has a major advantage over wetlands to the north, as its carbon market is open year-round. South Florida’s subtropical climate provides opportunity for year-round growth (and dieback) of plants, which leads to much more carbon investment in the peat soil.

This is great for our stocks, because instead of being released into the atmosphere during decomposition, carbon remains steadfastly in the soil bank. The peat in the Everglades isn't just a stockpile, it’s a goldmine made up of 30 to 45% carbon. In the Water Conservation Areas, for example, the peat soils have carbon stocks equivalent to 70 million homes' energy consumption for a year. The mangrove forests along the coast are another profitable account, sequestering and storing lucrative amounts of carbon valued at nearly $3 billion.

But like all transactions, there’s a fee to pay. These waterlogged conditions that are so good at soaking up carbon are also ideal for methane production, a potent greenhouse gas. While wetlands are a significant natural source of this compound, most methane emissions come from human activities.

Two types of soil found in the Everglades, peat soil (A) with 78% organic matter, and marl soil (B) with 14% organic matter. Source: Everglades Regional Environmental Monitoring and Assessment Program

The Bearish Past: Everglades Disturbance

Unfortunately, the Everglades’ carbon stocks have experienced a few bearish trends. Over the last century, about half of the Everglades was lost due to drainage and development, while the wetlands that remain are threatened by pollution, reduced freshwater flow, climate change, and invasive species.

Disturbance comes with a cost, fueling the loss of vast amounts of carbon stocks from the River of Grass. In particular, changes in hydrology led to quite a dip in the Everglades’ carbon investment portfolio. For instance, drainage and excessive drying of peat soils allows organic matter to decompose much more quickly than when it’s flooded, releasing carbon dioxide to the atmosphere. When water is above ground for shorter periods of time, less carbon is sequestered, as well. Finally, fires rapidly release carbon dioxide from the bank by burning vegetation and peat soils.

Source: The Everglades Foundation

If that weren’t enough, there’s a looming crash on the road ahead due to climate change. Sea level rise and the exposure of freshwater wetlands to saltwater can convert peat soils into sources of carbon. The drier conditions predicted under climate change could increase the risk of wildfires, dry-down, and exposure of peat soil to oxidation, and the release of more carbon dioxide assets into the atmosphere.

Grabbing the Bull by the Horns with Everglades Restoration

Luckily enough, the Everglades is benefiting from a strategic plan, the Comprehensive Everglades Restoration Plan, which aims to restore and preserve Everglades ecosystems. A main goal is to send more freshwater into the Everglades, particularly during the dry season, which is predicted to better protect existing carbon stocks while amplifying its capacity to sequester new carbon.

Although challenges remain for the sizable carbon banking potential of the Everglades, restoration provides a glimmer of hope for the current and future riches of the Everglades. More carbon in the soils of the Everglades will improve habitats across the Everglades, build soil elevation, and fight global warming. Let’s hope carbon stocks in South Florida compound over time…not in the atmosphere, but where they’re needed, in the soggy soils of the Everglades.

Source: International Mapping Associates, 2021


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