How Seagrass Can Solve Critical Environmental Problems
Did you know that the oceans absorb around 25% of the CO2 released into the atmosphere from human activities and this makes the oceans more acidic? This absorption of CO2 significantly helps humanity in its fight against dangerous climate change. However, according to a report from the Intergovernmental Panel on Climate Change entitled “The Carbon Cycle and Atmospheric Carbon Dioxide”, the “overall ability of surface seawater to take up CO2 decreases at higher atmospheric CO2 levels. The effect is large.” This is at a time when reducing atmospheric CO2 as much as possible is essential to avoid the dangerous implications of climate change. In addition, over the last 200 years, an increase in atmospheric CO2 has resulted in a 30% increase in seawater acidity. This has implications for humanity as well as some ocean species. Many economically and ecologically important ocean species such as corals, oysters, some plankton species, shellfish, and other species are at significant risk due to ocean acidification. The increase in ocean acidification over the last 200 years has been more rapid than that seen over the course of the past 55 million years and this means that species affected by ocean acidity may not know how to adapt to these increasingly acidic conditions.
Most say that ocean acidification and some other climate-related problems facing the oceans (and corresponding impacts on humans) can be reduced by reducing the carbon humans emit into the atmosphere but there is another noteworthy idea. This is the protection and restoration of seagrass marine plants. These plants are like prairie grasslands except that they are underwater and are among the most productive ecosystems on earth.
Advantages of Seagrass
Research published in 2021 in the journal Global Change Biology describes an extensive study of seven underwater seagrass meadows spanning 1000 km of the US west coast over 6 years. The research found a reduction in acidity in seagrass ecosystems in the majority of cases studied. Maximum reductions in acidity were found to occur in spring and summer seasons when seagrass species grow. The authors state that seagrass meadows can locally alleviate high ocean acidity “conditions for extended periods of time with important implications for the conservation and management of coastal ecosystems”. This can help the aforementioned economically and ecologically critical species which depend on less acidic conditions.
In addition to providing a local refuge from ocean acidity seagrass meadows have been noted to be able to absorb significant amounts of carbon. According to the organization ClientEarth “Seagrass accounts for 10% of the ocean’s capacity to store carbon, despite occupying only 0.2% of the sea floor. It can capture carbon from the atmosphere up to 35 times faster than tropical rainforests. One report by the Intergovernmental Panel on Climate Change (IPCC), observed that mangroves, salt marshes, and seagrass meadows can store far more carbon per hectare than most terrestrial ecosystems.”
The organization also states that “restoration of these meadows can count towards national climate change plans.” This is important for Canada given the significant prevalence of seagrass meadows in our coastal waters.
In addition, seagrass meadows protect coasts from the force of the sea during storms and from sea-level rise caused by global warming. They do this by, according to one description, “softening the force of the waves with their leaves.” This can significantly help coastal towns and cities fight storms which are predicted to become more prevalent due to climate change. Seagrass species support biodiversity by providing feeding grounds for thousands of species, produce natural compounds that kill the bacteria that can harm fishes, and help nutrient cycling by taking up nutrients from the seabed soil and releasing them into the water through their leaves.
According to a recent summary of seagrass published on the United Nations Environment Program website “conserving and restoring seagrass meadows can contribute to achieving as many as 10 of the UN Sustainable Development Goals as well as the goals of the Paris Agreement and the Convention on Biological Diversity.”
Seagrass Under Threat – What We Can Do
Unfortunately, according to one estimate published on the Smithsonian Institution website, “Seagrass coverage is being lost globally at a rate of 1.5 percent per year. That amounts to about 2 football fields of seagrass lost each hour. It’s estimated that 29 percent of seagrass meadows have died off in the past century. In a 2011 assessment, nearly one quarter of all seagrass species for which information was adequate to judge were threatened.”
The Canadian government needs to conserve and expand our coastal seagrass meadows because of the environmental services that they provide.
Research published in 2021 describes how seagrass species in Canada’s coastal waters are under threat as a result of human activities and what can be done to reduce this threat. Threats include coastal development, pollution, aquaculture, and fisheries activities. Here are some ways in which we can address these threats. New coastal and near-coastal developments (such as dredging to remove seabed sediments) need to be situated and designed to avoid harming seagrass species. Problems with human activities that deposit nitrogen into water bodies – known as nitrogen loading – need to be addressed. The authors of the research state that “It has been estimated that upwards of 64% of eelgrass meadows in Nova Scotia, New Brunswick, and Prince Edward Island are at risk of decline due to excess human-derived nitrogen loading”. Examples of sources of nitrogen loading include agricultural runoff, wastewater treatment facilities, and industrial plants. Aquaculture facilities also contribute to nitrogen loading. Nitrogen loading harms seagrasses by increasing phytoplankton growth as well as annual algae cover which both can block light from reaching seagrasses. Human induced nitrogen-loading near coastlines need to be identified with the intent of reducing this form of pollution. Also, bottom trawling activities – which drag nets along the seafloor to capture certain species such as fish but which can destroy other non-target species – in Canada’s waters should not be allowed in areas where there are significant seagrass meadows.
In 2009 the Canadian government designated eelgrass (which is Canada’s most abundant seagrass species) as an Ecologically Significant Species (ESS) to be prioritized for conservation and inclusion into new Marine Protected Areas. In addition, the Canadian government has committed to protecting 30% of our ocean areas by 2030. The federal government should move forward with this commitment and make sure that critical seagrass ecosystems are protected within this 30% goal by creating Marine Protected Areas in locations which currently have significant seagrass species but are outside of existing MPAs. To do this we need a national seagrass mapping assessment which provides the complete status and distribution of different seagrass species in Canada’s coastal waters. Targets are needed for the inclusion of seagrass species into Marine Protected Areas. We need to make sure the federal government fulfills its commitment to protect our oceans and ensure that critical species such as seagrass species are fully protected.
