Jim Salinger: Climate change, overfishing, a mammoth threat
It will be only a matter of time before the Paris Agreement will include the accounting of our marine emissions into the atmosphere, Dr Jim Salinger says. Photo / Greenpeace OPINION New Zealand has a huge Exclusive Economic Zone - spanning four million sq km - which is 15 times the land area of Aotearoa New Zealand, and is the fourth largest in the world. If we add in the extended continental shelf area, it is even larger. However, overfishing and habitat destruction due to local and regional threats are undermining fisheries, biodiversity, and the long-term sustainability of the ocean environment in our EEZ with liberation of large amounts of carbon dioxide emissions. A paper in Nature last month identified that fishers that trawl the ocean floor release as much carbon dioxide (CO2) as the entire aviation industry. Bottom trawling is where heavy nets are hauled along the seabed, releasing one gigaton of carbon per annum. This is released from the seabed sediment into the water, and can increase ocean acidification, as well as adversely affecting productivity and biodiversity. Marine sediments are the largest pool of carbon storage in the world. About two decades ago, bottom trawling was banned in areas that were impossible to trawl because of huge rocks and rugged ocean bottom, and zones that had already been overfished, forming Marine Protected Areas (MPAs). However, this left the other areas open to bottom trawling, releasing huge amounts of CO2 into the ocean environment. Recent work has also highlighted the importance of the ocean as a way of enhancing storing of carbon and notably the role of kelp in this process. Additionally, the Food and Agriculture Organisation (FAO) have calculated the amount of CO2 released per tonne of fish landed. Using 2012 landings, our marine emissions amount to an extra one million tonnes of CO2 annually over our EEZ. At the same time our ocean territory Is warming up. Over the period between 1854 and 2019, our EEZ has increased in temperature by over 1C. This will have a dramatic impact on our marine ecosystems, as well as fisheries. Warmer seas also drive the gas CO2 into the sea water turning it more acidic. It will be only a matter of time before the Paris Agreement will include the accounting of our marine emissions into the atmosphere. The sooner we ban bottom trawling in its entity over our huge EEZ, New Zealand would achieve large gains across three objectives: biodiversity protection, seafood production and climate mitigation. Let's do it. Professor Jim Salinger is a noted international climate scientist. It's been 22 years since the terrorist attack on the World Trade Centre in New York.