Mangroves are an important coastal plant. They prevent erosion and buffer coastlines against storm surges. Their dense submerged roots provide safe places for fish and shrimp and other creatures to breed. In an age of climate change and rising sea levels, they offer a form of ‘green infrastructure’ to help protect coastal communities.
Unfortunately, if you’re trying to develop a coastline for tourism or industry, then mangroves are impenetrable, inconvenient and mostly in the way. They get cleared, and sometimes it’s only once they’re gone that their benefits become more obvious. Consequently, mangrove reforestation projects are underway in many parts of the world, but they can be hard to replace.
A well established mangrove bush is robust, with multiple deep roots anchoring it into the sediment. Those roots also offer protection to young plants, protecting them from the wind and the waves while they get established. Without that protection, new propagules are at the mercy of the elements. If enough damage has been done to a mangrove ecosystem, it no longer propagates itself and goes into decline. New plantings will struggle to survive and it can be hard to reverse a mangrove ecosystem that has been compromised.
Palencia Lagoon in Belize, for example, had seen considerable development around the edges and mangroves cleared and replaced with sea walls and infrastructure for tourism. The local community and landowners recognised the importance of mangroves, but attempts to reforest them had largely failed. Survival rates for new plants were initially very low.
However, a relatively simple planting technique has made a big difference in Palencia Lagoon. The ‘Riley Encasement Methodology‘ plants mangrove propagules inside a length of PVC pipe, slit along its length and driven into the sediment. The plant gets enough light to grow upwards, and doesn’t start sending out its side roots until it reaches the top of the pipe. The result is wide spreading roots that anchor the young plant like the guy ropes on a tent.
After providing protection from the waves when it is most vulnerable, the pipe can then be removed, leaving behind a plant that can withstand the waves. Field tests have shown that REM plantings have a much higher survival rate, and make it possible to reforest coral islands and sandbars that would otherwise have been completely impractical.
REM mangrove reforestation projects are underway in a number of locations in Belize and elsewhere, with training workshops and support for community groups that want to use the technique.
Innovation is often associated with high tech, but I love a good story about simple, practical solutions from people tinkering in the field and finding something that works – in this case Bob Riley from Florida. These sorts of ideas get far less attention, but often do far more good in the long run. (Like the story of SRI rice, which is possibly my favourite out the 3,700 odd posts on the blog.)