Seagrass carbon Storage - marine biosequestration could be important for negative emissions

Updated 28 October.

Blue carbon is part of the solution to tackle climate change. So why aren't we talking about it far more?

Blue carbon refers to the carbon sequestration potential of coastal ecosystems: that zone reaching from just above the high tide mark to the coastal shallows. It includes salt marsh, mangroves and seagrass meadow ecosystems.

We need to take care and nurture our coastal ecosystems as they can play a vital role in bio-sequestration of carbon at rates far in excess of forests and soil carbon farming.

Biologists working with seagrasses met to present papers and discuss scientific practices at the 12th International Seagrass Biology Workshop (ISBW) (Conference website) in Wales 16th to 21st October. Just before the conference 122 scientists across 28 countries associated with the World Seagrass Association released a statement on the global importance of conserving and expanding seagrass meadows.

Guest Post: Reversal of sea level rise co-ordinated planning increasing risk to Australian coastal development

Sea level rise is perhaps one of the greatest perils of climate change over the long term according to Dr Peter Ward. The rate of rise will start relatively small and accelerate over this century and the following ones. The latest IPCC report projects sea level rise at 28-98 centimeters by the year 2100, and while this is more than the previous report, there is considerable doubt that this may be still unduly conservative. We simply do not know and understand the complexities of ice sheet disintegration - a non-linear process.

A survey of scientists researching in the sea level field - Expert assessment of sea-level rise by AD 2100 and AD 2300 - found that sea level rise is likely to be 70-120 centimeters by 2100 if greenhouse-gas emissions are not mitigated. A few like James Hansen think that it could be substantially higher.


The Postdam Institute for Climate Impact Research said in a media release:

The experts were also asked for a “high-end” estimate below which they expect sea-level to stay with 95 percent certainty until the year 2100. This high-end value is relevant for coastal planning. For unmitigated emissions, half of the experts (51%) gave 1.5 meters or more and a quarter (27%) 2 meters or more. The high-end value in the year 2300 was given as 4.0 meters or higher by the majority of experts (58%).

And yet here in Australia we see the Federal Government dropping the ball in co-ordinating coastal planning, and State Governments also withdrawing, leaving planning up to local Government which largely lacks the resources and cannot afford to carry the risk of inappropriate planning and development on our coasts. Queensland is just the latest Government to absolve itself of this planning responsibility.

Guest Post: Philippines steps up restoration of mangroves as defence against typhoons, tsunamis, sea level rise

Coastal ecosystems are important for providing a range of services that tend to be taken for granted, even ignored as coastal development is promoted at the expense of salt-marshes, mangroves, and seagrass meadows. One of the more important roles for salt-marshes and mangroves is as a natural shield against typhoons and tsunamis, such as Typhoon Haiyan which recently devastated parts of the Philippines. Restoring mangroves helps build resilience to these communities, providing jobs and income in the short to medium term, and providing the opportunity for long term sustainability as well as being significant blue carbon sinks. Lindsay Stringer, Professor in Environment and Development and Director of Sustainability Research Institute at University of Leeds, and Steven Orchard, PhD Candidate at University of Leeds, report:

Mangroves, nature's shield against typhoons and tsunami

By Lindsay Stringer, University of Leeds and Steven Orchard, University of Leeds

Following typhoon Haiyan, the Philippines’ Department for Environment and Natural Resources has earmarked around US$8m to fund efforts to replant much of the affected coastal zone with mangrove forests. Reforesting these coasts with 19m trees, particularly the extensively damaged islands of Leyte and Samar, is a key part of bolstering the first line of defence against future storms. Reports suggest up to 80% of the money is likely to be channelled to residents to engage them in tree planting activities as part of the country’s cash-for-work programme.

Seagrass projected to drastically decline with sea level rise

To most of us, what is hidden beneath the waves of our coastal environment remains invisible and is little thought about or cared about. Yet seagrass meadows, though hidden from our direct view, contribute valuable ecological services supporting valuable fish nurseries, as food for dugongs and turtles, and as a highly efficient blue carbon sink sequestering carbon.

A new study of the seagrass meadows in Moreton Bay, Queensland found that a significant proportion of valuable seagrass habitats would be lost without action to offset the affects of climate change. "The area of seagrass habitat was predicted to decline by 17% by 2100 under a scenario of SLR of 1.1 m." said the study.

Lead author Dr Megan Saunders from UQ's Global Change Institute said "Seagrass meadows not only help to slow climate change by sucking up a large portion of the world's plant-stored carbon, but they also benefit livelihoods, food security, fisheries, biodiversity, shoreline protection and other ecosystem services,"

Coastal Wetlands under threat from Sea Level Rise says World Bank

Climate change induced sea level rise of one metre is likely to destroy 60 per cent of the developing world's wetlands says a new World Bank research working paper. The economic loss of these wetlands is estimated at approximately $630 million US dollars per year.

The World Bank study looked at the risk to coastal wetlands in 76 countries at a sea level rise of one metre. Because there are so many uncertainties with the rate of sea level rise, the one metre level was chosen to study the likely impact. This sea level may be achieved this century, with sea level rising 60% faster than IPCC projections. Sea level rise is unstoppable, but it can be slowed through emissions reduction and give us humans and ecosystems a chance to adapt. Sea levels will continue to rise for several centuries.

The study found that about 99% of the coastal wetlands at elevations of one meter or less in the Middle East and North Africa could disappear, as well as 77% in sub-Saharan Africa, 66% in East Asia and 39% in Latin America and the Caribbean. Places like the iconic Sundarbans of Bangladesh and India, a major home and refuge to the Bengal tiger, are under threat.

Planners need to allow for Coastal wetlands migration due to sea level rise, climate change

Coastal Wetlands are under pressure. They face rising seas from climate change, but their biggest obstacle to migrate naturally inland is human development with roads, houses and other infrastructure blocking their way. And our urban planners are largely unaware of this tricky situation.

We all love to live beside the sea, but coastal urban development and rising seas will increasingly threaten sensitive coastal wetlands with no room to move and imperilling the survival of their unique plants, birds and fish.

Our urban planners have taken a stable sea level for granted with development to date, often destroying wetland environments for coastal development, agriculture and aquaculture.

More recent urban planning incorporating sea level rise predictions places an emphasis on the threat to peoples houses, roads, railway embankments and other human infrastructure. But planning also needs to encompass the coastal wetland environments that share our coastlines. These ecosystems will also need to migrate inland as the ocean rises.

See also: Mangrove Alliance | Mangrove Action Project | Mangrove Watch Australia | Coastal ecosystems suffer 100 fold decrease in capacity to store carbon mitigating climate change

California coast to be hit hard by sea level rise with climate change

A US National Research Council report released June 22 concluded that average global sea level is likely to rise two to three times higher within this century than previously estimated by the Intergovernmental Panel on Climate Change in 2007, with the US west coast being particularly affected at greater than the global average for sea level rise.

The study confirms that sea level rise is accelerating and is in accord with other recent studies estimating global sea level rise at a metre or more by the end of the century, with the melting of land ice now the largest component of global sea-level rise (about 65%). Scientists say that Global Warming means 20 Metre sea level rise is in the pipeline.

Related: Sea Level Rise and Australia | The risks of Sea Level Change - Dr Peter Ward | Scientists Estimate Sea level Rise for next 500 years

Seagrass meadows are key carbon sinks for combatting climate change

May 22 is UNESCO's
 International Day for Biological Diversity which focussed strongly on conserving our marine diversity. One of the important marine ecosystems are the seagrass meadows around the coasts of the world. A new global scientific research study just released has shown that seagrass meadows store significantly more carbon than any land based forest. They are very important as carbon sinks. But they are also suffering a major decline due to pollution from agricultural and mining development and chemical runoff, coastal development changing water turbidity upsetting photosynthesis in seagrass, and increasing sea surface temperatures affecting seagrass growth due to global warming.

The new global study of seagrass meadow ecosystems has found that coastal seagrass beds store much more carbon than can be stored in even the most carbon dense forests, such as the temperate native forests of Victoria. Seagrass meadows can store up to 83,000 metric tons of carbon per square kilometre, mostly in the soils below them. In comparison, a typical land forest stores around 30,000 metric tons per square kilometre mostly as wood. It is the first global study to analyze the carbon storage capacity in seagrasses.

Seagrass meadows support a highly level of biodiversity with many fish species using the seagrass during their juvenile period, as well as providing homes for crabs, sea urchin, seahorses shrimp and prawns. Sea tutles, dugongs and manatees depend on seagrass meadows as a primary food source. As Professor Carlos Duarte points out in an article on The Conversation website, Indigenous cultures new the significance and value of seagrass meadows. Conservation and restoration of seagrass ecosystems provides a unique Submarine Carbon Tax Opportunity! Seagrass meadows are intense, but fragile carbon sinks.

More Information: Seagrass Watch | Global Seagrass Monitoring Network

Coastal ecosystems suffer 100 fold decrease in capacity to store carbon mitigating climate change

The carbon sink capacity of urbanized river estuary and coastal environments to mitigate climate change has reduced by 100 fold according to scientists from the University of Technology Sydney. The Scientists used core samples from Botany Bay in Sydney to reconstruct the sedimentation changes in the past 6000 years, highlighting the changes in the ecology. The plant samples in the sedimentation changed as rapid industrialisation occurred around Botany Bay during the 1950s.

"We have effectively gone back in time and monitored carbon capture and storage by coastal ecosystems, finding a 100-fold weakening in the ability of coastal ecosystems to sequester carbon since the time of European settlement. This severely hampered the ability of nature to reset the planet's thermostat." said Dr. Peter Macreadie, University of Technology, Sydney Chancellor's Postdoctoral Research Fellow.