Kelp forests, which can be found at temperate latitudes along around 25% of the world’s coastlines, are essential to the health of the oceans. However, these swaying woods are disappearing quickly in specific regions of South Australia, the Baltic Sea, and Atlantic Canada as a result of human-induced climate change and other environmental stresses. Turf algae, a fast-growing opportunistic species that radically alters an ecosystem’s richness and structure, are gradually displacing the kelp forests in these areas.
Diverse varieties of seaweed that flourish in nutrient-rich, chilly water make form kelp forests, which are entirely submerged. These seaweed forests are extremely prolific despite lying below the surface, achieving “among of the greatest rates of primary production of any natural ecosystem on Earth.” In perfect circumstances, certain species can live up to 25 years. They also have a lengthy lifespan.
These hidden woods, according to Filbee-Dexter and Wernberg, are ecological engineers, altering the structure and operation of the very system they live in. The pH of the water, the amount of light available, and the water flow are all impacted by the kelp forest and its structure, which in turn influences the ecosystem’s rate of primary generation. Fish, crustaceans, urchins, and snails receive direct assistance from the forest, which also serves as a source of food. A secondary population outside the “bounds” of the forest receives habitat and nutrition from the massive volumes of drift material that kelp forests produce.
According to Filbee-Dexter and Wernberg, “these maritime forests are critically vital not just to marine flora and animals but also to humans.”
Today, kelp harvesting, commercial and recreational fishing, tourism, carbon sequestration, and coast preservation all benefit humans. However, our connection to the kelp forest is considerably older.
The authors write, “Evidence shows that early humans may have evolved along southern Africa’s rocky coasts as a result of a rich diet of marine creatures supported by extremely productive kelp forests.” And more recently, “early settlers of the Americas followed the ‘kelp highway’ along the Pacific Rim, supported by the bounty given by kelp forests,” according to research.
But as numerous studies have shown, these various ecosystems are in danger. More and more of them are going extinct as a result of human activity and climate change. The scientists note that kelp forests have been increasingly being replaced by turfs over the past ten years, transforming the reef seascape from a complex forest to a structurally straightforward mat of low-lying algae.
Despite being microscopic, turf algae have the power to completely devastate kelp-based ecosystems. Turfs can result in the loss of habitat, food, and production because they create thick, dense mats that alter sunlight and nutrient availability. Furthermore, “large-scale changes from kelp forests to turfs have not exhibited recovery, but reefs have stayed in a damaged turf state,” unlike kelp forests that collapse owing to increases in sea urchin populations (urchins will graze a forest to the point of destruction).
The reason for the seemingly irreversible change from kelp forests to turf algae, according to Filbee-Dexter and Wernberg, is unknown, but “human-driven environmental changes, such as ocean warming or coastal eutrophication, are favoring the growth and survival of turfs over kelps and decoupling the kelp loss and recovery processes from top-down control by urchins and/or their predators.”
From the Baltic Sea to South Australia, this transition from kelp forests to turfs is taking place all over the world. Since kelp grows best in calm waters, global kelp forests have experienced drastic reductions as a result of ocean warming and the myriad of issues it brings with it, including eutrophication, pollution, and invasive species.
According to the scientists, “Climate change has put Earth on a trajectory where more unique conditions and biological interactions have the potential to disrupt or disconnect many of the natural ecosystem drivers and feedback mechanisms maintaining otherwise very resilient kelp forests.” These modifications “may trigger long-term transitions to other ecosystem states that offer significantly different ecological services.”
More investigation on the variations in kelp loss across settings from the Atlantic to the Pacific is required in order to better protect and, ideally, restore these ecosystems. The creation of “a clearer causal and mechanical knowledge of what causes these transitions” from turf algae to kelp forests is equally important.
The authors write in their conclusion, “We have a limited window of opportunity to discover the processes that give resistance and stability in kelp forests or drive these transitions to turfs, and this information is vital to strategies to restore, recover, or avoid further degradation.