Sea urchins are spiny creatures that live on the ocean floor and feed on algae, especially kelp. Kelp forests are underwater ecosystems that provide shelter and food for many marine animals, such as fish, crabs, lobsters, and abalone.
However, in recent years, the population of sea urchins has exploded along the coast of Australia, due to warming waters and the decline of their natural predators.
As a result, they have been devouring the kelp forests and creating barren areas where only urchins and encrusting algae can survive.
This has serious consequences for the biodiversity and productivity of the marine environment, as well as the livelihoods of the people who depend on it.
The problem of the purple invaders
MENAHEM KAHANA/AFP via Getty Images
One of the main culprits behind the kelp forest destruction is the long-spined sea urchin (Centrostephanus rodgersii), which is native to temperate waters around New South Wales.
But as oceans heat up, their range has expanded more than 650 kilometers, through eastern Victoria and south to Tasmania.
Their numbers are increasing rapidly, with scientists estimating that there are now hundreds of millions of them along the eastern coastline of Australia.
The long-spined sea urchin is a voracious grazer that can consume up to 30 times its body weight in kelp per day.
Once the large kelp is gone, they switch to feeding on small encrusting seaweeds that can regrow quickly and resist intensive grazing.
This creates "hyper-stable" urchin barrens, where the urchins form dense aggregations and prevent the recovery of the kelp.
The loss of kelp forests has devastating effects on the marine ecosystem, as they support hundreds of species of fish, invertebrates, and seaweeds.
Some of these species, such as abalone and rock lobster, are commercially valuable and important for the local economy.
Kelp forests also provide ecosystem services, such as carbon sequestration, nutrient cycling, and coastal protection.
One of the ways to tackle the urchin problem is to eat them. Sea urchin roe, or uni, is considered a delicacy in many countries, especially Japan, where it is used in sushi and other dishes.
Sea urchin roe has a creamy texture and a sweet and briny flavor, similar to oysters or clams. It is also rich in protein, omega-3 fatty acids, and minerals.
In Tasmania, there is already a government-backed urchin fishery, which aims to reduce the urchin density and promote the recovery of the kelp forests.
The fishery employs divers who collect the urchins by hand and sell them to local and international markets. The fishery also provides jobs and income for the coastal communities.
However, eating sea urchins alone is not enough to solve the problem. Other measures, such as restoring the populations of sea otters and starfish, which are natural predators of urchins, are also needed.
Moreover, reducing greenhouse gas emissions and mitigating climate change are essential to prevent further warming and acidification of the oceans, which favor the urchins over the kelp.
Eating sea urchins is not only a way to help the environment, but also a way to enjoy a portion of delicious and nutritious food.
By supporting the urchin fishery and consuming more urchin roe, we can contribute to the conservation of the kelp forests and the marine life they sustain.
