Submerged biodiversity: from plankton to coral reefs and river currents, a vital network connects everything.
River basins collect and drain the land to transport nutrient rich fresh water that is vital to oceanic life. But this network of relationships, as represented in the theme of Slow Fish 2021: The Water Cycles, can be broken easily when activities on land damage the balance of nature.
Submerged biodiversity is at risk. In the second of our international webinars at Slow Fish 2021, Submerged Biodiversity: A Network of Connections, we explored how what happens on land affects life underwater. The testimonies of three guest speakers evidenced just how fragile the balance of nature is, what happens when human activity is left to proliferate without any thought for the environment, and what can be done to preserve this precious living heritage.
How the land feeds the sea
Dr. Nobuyuki Yagi of the University of Tokyo, Japan, began by underlining just how important the nutrients from land are for life in the sea. Indeed, the nutrient cycle is just one of the reasons why we’ve opted for the theme The Water Cycles, in the plural, at Slow Fish 2021: because there isn’t just one cycle transforming water vapor into clouds and rain and so on. The nutrient cycle is essential for marine life, as the photosynthetic organisms at the base of the marine food chain need nitrogen and phosphorous to grow. These nutrients are carried to the oceans by rivers.
As Dr. Yagi explained, rainfall facilitates the dissolution of land-based nutrients into river water, and insufficient nutrition in the water can lead to the death of seaweed species. But this isn’t what’s happening; quite the opposite. As agricultural activities intensify on land, with ever-growing use of chemical inputs like fertilizers, more and more nutrient-rich top soil is being washed away by the rain and being carried to the sea. This is a double disaster: both for the impoverished soil we use to grow vegetables on land, and for the marine life that suffers when there’s too much silt in the water.
One solution is to plant trees and other plants that help improve soil retention and decrease the amount that is washed away by rainfall. The Hokkaido Fisheries Cooperative Associations Women’s Group has been actively involved in this activity since 1983. Another solution being widely practiced off the coast Hokkaido is the use of sailboats when fishing in waters rich in seagrass, as motor-powered boats destroy the grasses and the habitat of several species, including shrimp. In Okinawa, no-catch zones have been established near coral reefs to allow pathways and pristine breeding grounds for fish species that are threatened. Once again, the use of plants on land to counter agricultural run-off draining excessive nutrients and silt into the ocean is being practiced, in particular through the use of shell ginger (Alpinia zerumbet), which is particularly good at improving soil retention. “These connections between the land and ocean reminds of the need for strong networks between people living in coastal and mountain areas,” Dr. Yagi concluded. “Long-term conservation activities must be encouraged over short-term commercial benefits.”
Ecological crisis in the Mar Menor
There were echoes of the same dynamics in the story of Jesus Gomez Escudero of Spain, a retired fisher who worked on the Mar Menor near Murcia. This 135km² semi-circular lagoon, which is never greater than seven meters deep, is separated from the Mediterranean Sea by a 22km sandbank. “There’s been a continuous reduction in the populations of the species that live in the Mar Menor. If in the 1970s there were 12 species with a healthy population, including the Mediterranean eel, but today there are only four. Sea breams alone account for the majority of the catch. We’ve witnessed mass die-offs of many other species, washed up along the beaches.”
As elsewhere, the changes to land use have had a devastating impact on marine life. “Climate change is accelerating processes that were already underway. The increasing quantities of nitrates and phosphates that make their way into the sea from agricultural run-off change the color of the water, and cause massive destruction when there is heavy rainfall. The floods of 2019 brought a lot of sediment into the sea, killing massive amounts of fish.”
The urbanization of the Spanish coastline to cater for foreign tourists since the 1980s are one of the long-term drivers of this problem, as is the increasing industrialization of agriculture with all the resultant problems regarding pollution of the soil and waterways. Yet to date there is no mass movement combating these trends – something Jesus laments: “Raising awareness of the scale of the problem among the local population is the first step we have to take if are to reverse these dangerous trends.”
Mangroves: havens of biodiversity
Pisit Chamsnoh of Trang, Thailand, has been working with communities across the southern part of his country for many years to restore mangrove ecosystems. These fishing communities in the Malay peninsula are among the poorest in the country, and are dependent on natural coastal resources. The mangroves are a particularly important element in this ecosystem, and their fate will determine the fate of innumerable other species, including humans.
“Our group, the Yadfon Association, started talking to people about how to protect the mangrove forests and began putting projects into actions together with government experts. The mangrove forests must be restored to their former state to ensure the well-being of communities, and that’s the basis behind all our actions, from planting new plants to stopping fishing activities in certain areas to allow stocks to recover. We all understand the connection between the mangroves and seagrasses. You can’t protect one without protecting the other. Fishing activities can easily damage seagrass meadows. Now the situation is slowly improving, and we’re expanding the project to communities in other regions beyond Trang.”
These direct actions along the coast will not be enough to swing the balance decisively in the favor of long-term ecosystem renewal and environmental conservation. “Protecting the sea beings in the mountains,” as Pisit puts it. “We need a political movement that takes into account all the activities on land, from the palm forests to the rivers, where we identify all the activities which are polluting the seas and impoverishing the soil. We must strengthen the land, and the benefits to the sea will flow quite literally in the waters of cleaner rivers.”
by Jack Coulton, email@example.com