Naturally-occurring giant kelp beds and seagrass meadows which grow offshore absorb the carbon and other greenhouse gases which scientists believe are leading to global warming, ice cap melt and sea level rise.
Creating more marine reserves and consciously encouraging the expansion of marine forests would enable countries like New Zealand to limit the global impact of their greenhouse gas emissions and reach greenhouse emission reduction targets, Emeritus Prof Ben Boer, from the University of Sydney, said yesterday.
Prof Boer, who is at the University of Otago this week, is the 2011 New Zealand Law Foundation's distinguished visiting fellow. He is touring five New Zealand universities speaking to staff and students and giving public lectures.
Now retired from full-time teaching, he is a guest lecturer at many universities and a consultant to several Australian and international conservation groups.
New Zealand is one of 91 countries or states which have signed the Kyoto Protocol - a pledge to bring greenhouse gas emissions down to 1990 levels.
Signatories could do that in two ways, Prof Boer said - by reducing emissions through measures such as reduced vehicle use and energy efficiency, and by adopting natural solutions such as planting more trees to absorb emissions.
Marine forests could theoretically be included in a country's greenhouse gas inventory alongside terrestrial forests, he said.
"Marine forests have huge potential for any country which has a long coastline, but particularly for those such as Australia and New Zealand where naturally-occurring kelp beds already grow."
Marine forests could be a money earner too.
Countries with abundant vegetation can trade carbon credits with those which do not have have enough vegetation to absorb all the greenhouse gas emissions they produce.
A recent New York Times article estimated the global carbon trading market was now worth an estimated $US30 billion ($NZ38 billion) and could grow to $US1 trillion within a decade.
Prof Boer said trading carbon credits from marine forests was a possibility.
"It seems to me that the system of using remote sensing mapping via satellite [to] measure the amount of carbon in forests from the air ought also to be able to be done in the marine environment."
Prof Boer favoured "natural solutions" such as protecting land and marine environments and an integrated approach to addressing climate change.
"At the moment, 11.5% of land area globally is protected in some way and the plan is to increase that to 17% over the next nine or so years. Less than 1% of the marine environment is protected and the plan is to increase that to 10%.
"The big challenge for environmental policy makers and environmental lawyers is how the achieve those targets. It involves politics, economics, economics, science and law."