Why we should care more about our coasts: coral reefs, mangroves and seagrass meadows in the tropics
By Hanna Sundahl
When you think of a tropical ocean, you probably think of pristine, turquoise waters, with colorful reefs spread below the surface teeming with fish and other stunning marine life. Indeed, this is what a healthy tropical coral reef should look like. Even though coral reefs cover less than 0.1% of the ocean surface area, they sure pack a punch in terms of biodiversity, with vertebrate species densities far greater than those found in rainforests (Kaiser, et al., 2011).
The coral reef at Heron Island, Great Barrier Reef, in all its splendor. (c) Sarah Norris, Published in Voyeur January 2014. Retrieved from: https://travel.virginaustralia.com/nz/voyeur/heavenly-heron-island
Coral reefs are a vital habitat for a number of reasons. Not only do they provide food, shelter and breeding grounds for marine life, reefs are also important for us people, since not only do they give us food (in many areas fish is the main source of protein), they also slow down wave action and serve as inexpensive coastal protection (Hoegh-Guldberg, et al., 2007). Coral reefs also have the potential to replace rainforests as the new “medicine cabinet” of nature to provide natural chemicals that can treat all sorts of human ailments (National Oceanic and Atmospheric Administration). And of course, they attract millions of tourists coming to dive and snorkel, making them a very important source of income for coastal regions (IPCC, 2014).
However, coral reefs are only part of the picture. They also have less well-known “sister ecosystems”, namely the muddy-looking mangrove forests and the seemingly simple-looking seagrass meadows. These habitats provide essential nursery spots for the juveniles of many of the fish we see while diving in coral reefs, including sweetlips, snappers, and surgeonfish (our beloved Dory) (Nagelkerken, et al., 2000). With their complex root systems keeping sediments in place, mangroves and seagrasses also help serve as coastal protection (Kaiser, et al., 2011).
Mangrove forest in Papua, Indonesia. (c) Photo credit: Ethan Daniels. Retrieved from: http://blog.nature.org/science/2013/10/11/new-science-mangrove-forests-carbon-store-map/
Seagrass meadow with predatory fish lurking above. (c) NOAA, Heather Dine. Retrieved from: http://www.amnh.org/education/resources/rfl/web/oceanguide/key.html
These three connected habitats are havens of biodiversity, sources of food and security for people, and all of them are unfortunately threatened by human coastal development. Mangroves and seagrass meadows suffer from chemical runoffs from shrimp aquaculture and farming nearby, as well as from outright mechanical destruction for land reclamation (American Museum of Natural History). Coral reefs also suffer from farmland fertilizer runoff that can cause eutrophication, leading to a habitat dominated by fast-growing algae rather than coral (Hoegh-Guldberg, et al., 2007). Careless tourists kicking and removing corals and associated living organisms, and irresponsible fishing practices like dynamite and cyanide fishing, add further pressures to these fragile ecosystems.
Considering their importance and vulnerability, protective measures need to be taken for these habitats. One such measure is to create strictly regulated Marine Protected Areas (MPAs), where limited or no human development can occur, and where visitors have to be extremely careful and considerate (National Oceanic and Atmospheric Administration). Such protected areas act as a refuge, a safe space in which biodiversity thrives, and act as a source population for re-colonization of surrounding habitat. Top priority areas are those with high endemism, where the habitat is still very intact, or that are important for feeding and breeding of long-distance migrators like manta rays or whales. The cost of maintaining MPAs is outweighed by their increased attractiveness for responsible divers and tourists in love with these healthy marine habitats.
MPAs, together with other regulations such as fishing quotas, can allow future generations to acquire the protein they need from the sea, live at the coast, and thrive on responsible tourism. Of course, there are global threats that cannot be kept out of these parks – notably ocean warming and acidification – which is why we also need to pay attention to our carbon emissions problem, the topic of my next post. But with this, I, as a diver and marine biologist, urge you to be a responsible tourist and citizen of the world and care about these fragile, yet incredibly important habitats.
References
American Museum of Natural History. (n.d.). Mangrove Threats and Solutions. Retrieved from Mangroves: the Roots of the Sea: http://www.amnh.org/explore/science-bulletins/bio/documentaries/mangroves-the-roots-of-the-sea/mangrove-threats-and-solutions
Hoegh-Guldberg, O., et al. (2007). Coral Reefs Under Rapid Climate Change and Ocean Acidification. Science, 318(1737), 1737-1742.
IPCC. (2014). Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. Geneva: IPCC.
Kaiser, M. J., et al. (2011). Mangrove Forests and Seagrass Meadows. In Marine Ecology: processes, systems, and impacts (2nd Ed) (pp. 277-303). New York: Oxford University Press.
Kaiser, M. J., et al. (2011). Coral Reefs. In Marine Ecology: processes, systems, and impacts (2nd Ed) (pp. 305-323). New York: Oxford University Press.
Nagelkerken, I., et al. (2000). Importance of Mangroves, Seagrass Beds and the Shallow Coral Reef as a Nursery for Important Coral Reef Fishes, Using a Visual Census Technique. Estuarine, Coastal and Shelf Science, 31-44.
National Oceanic and Atmospheric Administration. Marine Protected Areas. Retrieved from http://oceanservice.noaa.gov/ecosystems/mpa/
National Oceanic and Atmospheric Administration. Medicine. Retrieved from NOAA Coral Reef Conservation Program: http://coralreef.noaa.gov/aboutcorals/values/medicine/
So glad you wrote about this topic, and I agree with what you are writing. Only one thing though, that I noticed when I was working in Indonesia (and as you surely noticed when you where there as well), is how many of the locals have a typical «live life one day at the time»-kind of mindset, where their main priority is to have enough food for that day/tomorrow, and don’t really think years or decades ahead. As you mentioned, locals using techniques as bomb fishing and cyanide fishing damage the coral reefs and thus the biodiversity, but what do you reckon needs to be done to change their way of thinking? I’d say education is key, but to be fair, its hard to change the way someone’s been thinking for their entire life – you can’t really go about worrying about the biodiversity in the sea if bigger worries like having food for yourself and your family is a daily struggle… So do you reckon alternative incomes/food sources would be the way to go? Or to provide fishermen with fishing gear that might be more efficient and at the same time non-damaging to the coral reefs and the biodiversity?
Great blogpost! This is a subject that should have more focus than it has. I also like the fact that you are describing WHY we should care, and not only how to care. This is in my opinion one of the main problems to why people don’t care, because they don’t know why. So that is great!
Furthermore, it seems like you have done great job on this subject, which I didn’t know that much about. Thank you!
Fantastic blog post, I am happy someone brought this up, as these are areas of immense importance, most people are concerned for the coral reef but you rarely hear about the value of the mangroves and sea grass beds (All are important habitats for my Sea slugs!). I especially liked that you took the view point of the organisms and biodiversity as a whole in to consideration as well as the values of these areas to humans. Many take a far to antoposentric view on conservation of organisms and habitats, mostly focusing on the services it provides to us, but this is also an important point. We are here and we are likely not going anywhere, and to gent people involved in saving biodiversity, we need to convey a direct value of it to the people living close to it. This is one of the cases that come to mind: http://www.sciencemag.org/news/2014/09/new-military-base-could-seal-fate-okinawa-dugong. When I was in Okinawa last year, there was a protest just outside the proposed building site of this base, many of the protesters, were locals that opposed the destruction of these unique habitats, but a fair amount were fishers who feared that their livelihood and the poulations of their prey, would be decimated by the building.
Also as you said it is especially important to protect the areas high in endemism and that are relatively intact. Even if we try to revive some areas, it may take a long time before things are back to normal (if ever). One example is by Zvonareva et al. (2015) (http://link.springer.com/article/10.1186/s40555-015-0120-0) who looked into snail assemblages in replanted mangroves versus intact mangroves, and even after ten year the planted mangroves were still inhabited mostly by generalist species whereas specialists still were found in the natural mangroves.