Coastal ecosystems – Threats and challenges
Article written by Venetia Galanaki.
Mangrove forests, seagrass meadows and saltmarshes, collectively referred to as coastal ecosystems, are some of the most valuable habitats on the planet, yet they are being lost at alarming rates. With approximately half of the Earth’s population residing on the coastal zone, anthropogenic (meaning caused by humans) pressure on these ecosystems is much higher compared to more remote habitats. On a global scale, the annual rate of decline has been estimated to be 1–3% for mangroves, 2–5% for seagrass meadows, 1–2% for saltmarshes. If this trend continues at the same rate over the next 50 years, only 15% of area covered by coastal ecosystems will remain compared to the coverage at the end of World War II. Estimating loss is a tricky business as historical data are limited and more often than not highly inaccurate. However, what is worrisome is that the rates at which we are losing these important ecosystems seem to be accelerating despite the recognition of their invaluable ecosystem services.
Numerous and often interconnected factors have led to this decline.
- Coastal development and Tourism: construction of pipelines, structuring of ports and deployment of cables for communication, has made the complete removal of these ecosystems common practice. Infrastructure built to accommodate the rapid increase of the tourism industry is leaving no room for these ecosystems. In addition, tourism related activities such as anchoring over seagrass meadows and the mere overcrowding in coastal areas is intensifying the pressure. Mangroves also suffer from overharvesting as their wood has a number of uses.
- Land runoff and Pollution: Due to their close proximity to agricultural land, coastal plants are threatened by land large amounts of fertilisers and pesticides that end up in the water and can ultimately cause their death. The damage caused by runoff is further intensified In river estuaries where water is carried from large stretches of agricultural land. Additionally, specifically for seagrass meadows untreated sewage waste and aquaculture can be really harmful due to the load of organic matter in the water.
- Invasive species also majorly impact these ecosystems as they can alter food webs and destabilise the entire ecosystem.
- Climate change related phenomena, primarily sea level rise, majorly affects the long term health of these ecosystems. Mangroves are damaged by excessive water in their roots and destabilisation of their sediment. In seagrass meadows, rising sea levels prevent the necessary light needed for healthy seagrass growth. Saltmarshes are usually constrained by human made structures and so sea level rise forces their area cover to decrease in a process known as coastal squeeze. Mangrove health is also intricately connected with coral reefs as they shelter them from strong currents. Reefs, being further offshore, constitute the first barrier for strong currents and waves and so when they are damaged, mangroves are more susceptible to them.
The vast majority of threats occur on a local level and can be minimised through efficient coastal planning and management. Eliminating local threats and, thus allowing ecosystems to be healthier, can help build resilience against the more widespread effects of climate change. Sadly, the destruction of these ecosystems is often “justified” as a means to generate profit. However, such decision-making neglects the fact that the mere existence of coastal ecosystems greatly contributes to the economy through the ecosystem benefits that they provide, such as protection from storm surges and sea level rise and support of local livelihoods. In recent years, the efforts to conserve our coasts have intensified and the laws and regulations protecting them have strengthened. Yet, until bold commitments are made they will continue to decline at the rates we see today, leaving humans and wildlife at a loss.
About the author: Venetia comes from Greece and the Mediterranean sea has always been her happy place. A Biomedical scientist turned conservationist, whose love for the ocean led her to pursue a career in protecting it. Over the years, she has conducted fieldwork in a variety of fields, including dolphin bioacoustics, marine pollution and seagrass carbon. She currently works in Marine Protected Area planning and management in Greece.
Reference: Duarte, C.M., Dennison, W.C., Orth, R.J. and Carruthers, T.J., 2008. The charisma of coastal ecosystems: addressing the imbalance. Estuaries and coasts, 31(2), pp.233-238. Full article here.