Mangrove forests are among the most productive ecosystems on Earth. Bridging the gap between land and sea, these forests function as important habitats for organisms of all shapes, sizes, and ecologies. From a purely structural standpoint, mangrove forests are vital for stabilizing coastlines, reducing erosion, and minimizing damage from storm surges. They are also extremely important habitats for carbon sequestration.

The key component of the carbon storing abilities of mangrove forests involves the formation of peat. Whereas we tend to think of bogs when we think about peat, mangroves form it as well. Peat is the result of the accumulation of partially decomposed vegetation and other organic matter. It’s the partially decomposed part of peat that makes it a major carbon store. Because it doesn’t decompose, all of the carbon locked up in the organic matter stays there instead of entering back into the atmosphere.

As they grow, the roots of mangrove forests accumulate debris and sediments, which builds and builds over time. As the organic layer grows, mangroves grow upward on their propped roots. Over decades and centuries, massive quantities of peat can develop under mangrove forests. This is also one of the ways by which coastal land develops. Needless to say, mangrove forests are extremely important ecosystems.

Photo by Phils 1stPix Licensed under CC BY-NC-SA 2.0

Sadly, because they occur along the coast, mangrove forests the world over have been degraded and destroyed at unsustainable rates. As these forests are razed, the land supporting them erodes, removing all of the accumulated sediments and peat. Not only does this destroy all of the ecological and economic benefits of mangrove forests, it also releases huge quantities of carbon.

In recent years, humans have finally begun to realize the environmental and economic costs of mangrove destruction and many regions are starting to implement mangrove restoration efforts. However, the success of any restoration can sometimes take years or even decades to fully assess. This is where chronosequences come in. By studying mangrove restoration projects at different stages of development, scientists can better understand mangrove restoration efforts over relatively short time periods instead of having to wait for individual projects to age to collect all of their data.

Recently, researchers in Florida decided to look at peat accumulation in various mangrove restoration projects. They looked at mangrove restorations of various ages, spanning 25 years of effort. They found that soil and peat accumulation in these forests is surprisingly rapid. In terms of soil accumulation, restored mangrove forests kept pace with and even outpaced natural mangrove forests within the first 5 years of restoration. Even more exciting, peat accumulation in these restored mangrove forests was very rapid, occurring within only a decade of the completion of a mangrove restoration attempt. When you consider the fact that each of the restoration projects they studied started in nothing but pure sand, these results are extremely encouraging.

The scientists point to mangrove roots as the main driver of soil and peat accumulation in these restored forests. As mangroves grow, their roots expand into the surrounding sand. As roots grow and die, they leave all of that organic matter in the soil. Also, the more roots there are, the more debris like wood, leaves, and sediments get trapped in and around the mangroves. This is why peat accumulation occurs so rapidly. What’s more, as sediment and peat builds up below the mangroves, their height increases. At current, the increase in height of these restored mangrove forests is outpacing the rate of sea level rise in coastal Florida. These are encouraging results when one considers just how fast these coastal habitats are changing as our climate continues to change.

The authors of this research are quick to point out that the fast rates of peat accumulation and mangrove growth are likely to slow as these ecosystems mature. Eventually, many of these processes are likely to balance out. They estimate that it would take at least 55 years for mangrove restoration projects in Florida to match their natural counterparts in terms of ecosystem services. Nonetheless, many components of healthy mangrove ecologies, like herbaceous and juvenile vegetation layers, are already established in restorations long before that 55 year mark.

These results are very exciting. Though there is no substitute for protecting natural mangrove forests (or any wild space for that matter), we need to start putting the pieces of our planet back together. If these data are representative of mangrove restoration efforts across the world, there is hope yet that we can replace at least some of what has been lost. Still, until more of the human race starts to value protecting wild spaces and the species they support, we stand to loose so much more. Support your local land conservancy today!!

Photo Credits: [1] [2] [3]

Further Reading: [1]

Photo by JJ Harrison licensed under CC BY-SA 3.0

What would you say if I told you there was a connection between dams and the damage coastal communities are faced with after a storm surge? It may not seem obvious at first but as you will see, plants form a major connection between the two. Now more than ever, our species is dealing with the collective actions of the last few generations. Rare storm events are becoming more and more of a certainty as we head deeper into a future wrought with man-made climate change. The reality of this will only become more apparent for those smart enough to listen. Rivers are complex ecosystems that, like anything else in nature, are dynamic. Changes upstream will manifest themselves in a multitude of ways further downstream.

The idea of a dam is maddeningly brilliant. Much like our cells utilize chemical concentration gradients to produce biological power, we have converged on a similar solution to generate the electricity that powers our modern lives. A wall is built to block a waterway and store massive quantities of water on one side. That water is then forced through a channel where it turns turbines, which generate power. The problem is that the reservoir created to store all of that water drowns out ecosystems and the organisms that rely upon them (including humans).

Here in the United States, we got a little dam crazy in the last few decades. With an estimated 75,000 dams in this country, many of which are obsolete, these structures have had an immense impact. One major issue with dams is the sediment load. As erosion occurs upstream, all of the debris that would normally be washed downstream gets caught behind the dam. Far from merely an engineering issue, a dams nature to trap sediment has some serious ecological impacts as well.

Until humans came along, all major rivers eventually made their way to the coast. A free flowing river continually brings sediments from far inland, down to the mouth where they build up to form the foundation of coastal wetlands. Vegetation such as sedges, grasses, and mangroves readily take root in these nutrient-rich sediments, creating an amazingly rich and productive ecosystem. Less apparent, however, is the fact that these wetlands provide physical protection.

Photo by HiGorgeous licensed under CC BY 3.0

Storm surges caused by storms like hurricanes can send tons upon tons of water barreling towards the coast. In places where healthy wetland vegetation is present, these surges are absorbed and much of that water never has a chance to hit the coast. In areas where these wetlands have vanished, there is nothing stopping the full brunt of the surge and we end up with a situation like we saw following Katrina or Sandy and are facing now with Harvey and Irma. Coastal wetlands provide the United States alone with roughly $23 billion in storm protection annually.

These wetlands rely on this constant supply of sediment to keep them alive, both literally and figuratively. As anyone who has been to Florida can tell you, erosion is a powerful force that can eat away an entire coastline. Without constant input of sediment, there is nowhere for vegetation to grow and thus coastal wetlands are rapidly eroded away. This is where dams come in. An estimated 970,000 km (600,000 mi) of rivers dammed translates into a lot of sediment not reaching our coasts. The wetlands that rely on these sediments are being starved and are rapidly disappearing as a result. Add to that the fact that coastal developments take much of the rest and we are beginning to see a very bleak future for coastal communities both in the US and around the world.

Photo Credit: [1] [2] [3]

Further Reading: [1] [2] [3] [4]