Science, Now + Beyond

We’ll lose the world as we know it if this grass dies out

The reality is pretty terrifying.

An often overlooked organism in the oceans may actually be responsible for much of our planet’s health. Unfortunately, like so many of the world’s important species, this one seems to be dying out at an alarming rate. It’s not the coral reef this time, it’s seagrass.

On the ocean floor, circling every continent except Antartica, are vast meadows of seagrass. Currents and waves send ripples through the grass much like a soft breeze on a prairie. They aren’t the most beautiful species in the sea, a lesser known cousin of seaweed, but seagrass plays several vital roles in the health of our oceans.

In most conversations about sea species and climate change, more attention is given to the depletion of corals and mangroves. Scientists are now pushing the public to focus more on seagrass, which has recently been identified as a key species in protecting our world’s waters and the many species that live in them.

These meadows act as a nursery to tiny fish eggs and protect young fish from predators as they grow to full size. Without seagrass, key parts of the food chain would be missing, affecting some of our favorite species like killer whales.

seagrass acts as a nursery to little fish

Dr. Joleah B. Lamb at Cornell University calls seagrass “the ugly stepchild of marine organisms,” because it is often ignored. But, the history of seagrass evolution is a fascinating one. Over the course of millions of years, seagrass’s unique ability to take root in deadly sediment, full of hydrogen sulfide, transformed the seabeds into a productive ecosystem full of life. By pumping oxygen into the soil, it became less toxic and allowed other plants to flourish as well. Seagrasses are resilient and can flower and undergo photosynthesis even in the dim light of deep waters, up to 190 feet.

Humans rely on the health of this key species, too. Our fishing industry depends on the haven these grasses provide to fish. The University of Cambridge estimated that each acre of seagrass benefits the industry about $87,000 per year. As a natural filter species, as well, seagrass filters out fertilizer runoff and other pollutants, worth about $11,000 per acre each year.

On top of that, which already makes seagrass the most economically valuable ecosystem on Earth, the plants also help us to remove pathogens in the water. This unique capacity means that marine organisms that live near seagrass meadows have reduced exposure to bacteria that cause disease. By protecting key species like coral and small fish that would be more susceptible to these pathogens, seagrass naturally preserves the health of underwater ecosystems.

seagrass is a key species that helps humans more than we know

But, they are disappearing at the astonishing rate of one football field every half hour.

What is causing the rapid decline of this key species? Climate change means increased temperatures and acidity in the water, which leads the seagrass to lose more oxygen through their leaves instead of their roots. Without enough oxygen being pumped into the ground through the roots, seagrass is dying because the soil is too toxic.

Runoff from construction and sediment built up on the shore means cloudier waters for seagrass. Reduction in clarity means limited sunlight gets to the seagrass leaves, leaving them less productive and therefore unable to produce as much oxygen. Again, this reduces the seagrass’s ability to detoxify the soil, causing die out.

Some communities give us hope in what feels like a dire situation. In Virginia, efforts are being made to restore large swaths of seagrass off the coast. There are now over 6,000 acres of it where there used to be none.

Even you can help! Call your representatives and local leaders to demand responsible legislation to combat climate change. Find local organizations that contribute to restoring endangered and threatened species like seagrass. Each donation and hour spent calling or volunteering truly does make a difference!