Macau Matters | Get your seaweed here

Richard Whitfield

Climate change, population growth, agricultural and other wastes and other problems are making our planet uninhabitable for humans. Luckily, seaweed can help us, but it will not solve all our problems.

Oceans cover 70% of the Earth’s surface and comprise 95% of available living space. Unfortunately, rising global carbon dioxide levels are heating up the oceans and making them more acidic. Human over-fishing has also decimated global fish stocks. We are dumping immense volumes of waste plastics that destroy habitats into all our oceans, and agricultural run-off is increasing ocean nitrogen and phosphorus levels, which is promoting the growth of toxic red tide algaes, etc.

Human action has already killed off 50% of the world’s coral reefs and will probably kill the remaining ones before 2050. Reefs are a key part of the ocean’s ecosystems, being home to over 1.4 million marine species and essential breeding grounds for fish and other sea animals. Using selective breeding and other techniques, scientists are starting to learn how to “encourage” reefs to survive in hotter and more acidic waters, but it is early days in these efforts.

We seem to be very successfully destroying our oceans, which are a major global resource – a “Tragedy of the Commons” writ large.

When people talk of aquaculture they often forget lowly seaweeds. But they have always been an important part of the human diet, and the value of human (and other animal and plant) consumption of seaweed is becoming more recognized globally. World annual production doubled between the years 2000 and 2014 to 27Mt, and a great deal more could be grown in the future.

Seaweed has a long history in Asian cuisines, where over 30 types are commonly eaten. As well as being useful food for humans, seaweed can be used as a plant fertilizer, animal feed, biomass fuel and as a source of hydro-colloids (used in cosmetics). Amazingly, Australian scientific studies are showing that including 2% of a common seaweed called asparagopsis taxiformis in the diet of ruminants (cows, sheep, goats) can reduce the waste methane gas that they excrete by over 80%. Methane is another dangerous global warming gas, like carbon dioxide, and is what we burn in gas cooking.

Seaweed cultivation also has other non-nutritional benefits. It does not take up land needed for food production, is easy to grow and does not need fertilizer or pesticides – it actually absorbs the nitrogen and phosphorus from agricultural run-off. It also absorbs much more carbon than land plants and, like land plants, produces oxygen. Large kelp and other seaweed beds are also very healthy and safe fish and crustacean nurseries, and can help replenish global aquatic animal stocks. And, finally, they moderate sea storms and wave action to reduce coastal land erosion.

All round, lowly seaweed is very useful stuff! It is not a magic bullet to save the world from global warming or ocean pollution, but it can be a significant element in solving both these problems.

Given the small size of our coastal waters, Macau is not well suited for seaweed production but we could certainly promote its use as a food. We can also encourage nearby regions to increase their seaweed production and use. The large quantities of food purchased to support our large tourism industry gives Macau strong leverage over nearby farming practices if we can find the will and expertise to use it wisely.