83 % of the global carbon cycle is circulated through the oceans. Coastal habitat contains 2% of the total ocean area, but account for approximately 50% of the total carbon sequestered in ocean sediments.
Blue Carbon is a recent concept which is increasingly being recognized as the most cost effective method to mitigate CO2 in adaptation to climate change. It supports ecosystems management and enhances natural resource values by restoring coastal habitat such as mangrove forests, sea-grass meadows and saltwater marshes.
It has a prominent presentation in the latest report by the Intergovernmental Panel on Climate Change with picture of mangrove restoration on its front page, which illustrates its importance in recent climate change efforts. The marine biosphere is a major component to the global carbon cycle, responsible for around half of the annual photosynthetic absorption of the green house gas (GHG) carbon dioxide (CO2) from the atmosphere. (Field et al. 1988, adapted from Lutz et al. 2007). It is high time to utilize its cost effective potentials with mitigation as an urgent need to reduce carbon in the atmosphere in addition to reduce emissions to secure global climate change targets.
The proposal to establish mangrove parks in Myanmar is a pioneering initiative in line with newly energized global efforts, as stated in abstracts from a few selected papers by UNEP, IPCC, Blue Carbon Initiative and others:
BLUE CARBON INITIATIVE
The role of coastal ecosystems in climate change mitigation
Fifty-five per cent of the atmospheric carbon captured by living organisms – as UNEP’s 2009 report ”Blue Carbon Greenhouse gas emissions from human activities are changing the world’s climate and reducing them, is at the centre of current climate change discussions. However, the critical role of oceans and their ecosystems has been vastly overlooked.
– The role of healthy oceans in binding carbon” noted – is taken up at sea. Between 50-71% of this is captured by the ocean’s vegetated “Blue Carbon” habitats – mangroves, salt marshes, sea-grasses, and seaweed – which cover less than 0.5% of the seabed, but therefore play an important role in the world’s climate and in mitigating change. These habitats, the report adds (while highlighting the considerable uncertainty surrounding estimates, and the level of understanding of their carbon storage) sequester between 114 and 328 Teragrams of carbon per year. Another 2009 report, by Laffoley and Grimsditch, synthesized current scientific information on carbon sequestration in coastal ecosystems and highlighted their importance in the global carbon cycle (www.iucn.org/dbtw-wpd/edocs/2009-038.pdf). UNEP and IUCN collaborated in publishing both these reports, which complement each other in providing general information and highlighting the considerable gaps in knowledge on the value of coastal ecosystems for sequestering carbon. Further seminal reports by the World Bank and Duke University have further highlighted the importance of coastal ecosystems in mitigating climate change.
These rates of carbon sequestration and storage are comparable to and often higher than rates in carbon rich terrestrial ecosystems such as tropical rainforests or peat-lands. Unlike most terrestrial systems, deposition of carbon dioxide in coastal ecosystem sediment can continue over millennia. Current rates of loss of mangroves, sea-grass beds and salt marshes, driven largely by human activities such as conversion, coastal development and over harvesting are more than twice as high as the rate of rainforest loss. This is of considerable concern with respect to their role in carbon sequestration and emissions.
Halting the decline of the Blue Carbon sinks is a missed opportunity in the current portfolio of climate change mitigation strategies. At the moment, there are no international regulatory frameworks or conventions to protect the value of coastal and marine ecosystems for sequestering carbon and mitigating climate change. Maintaining and managing Blue Carbon ecosystems both provides the global community with an additional tool for mitigating carbon dioxide concentrations in the atmosphere, and maintains the valuable ecosystem services they supply to local communities – including protection against storm surges and sea-level rise (important for adaptation to climate change), food security gained from fisheries, revenue from tourism and the potential medicinal value of wild species.
WHAT IS BLUE CARBON?
The problem: The growing emission of carbon dioxide from a wide range of human activities is causing unprecedented changes to the land and sea. Identifying effective, efficient and politically acceptable approaches to reduce the atmospheric concentration of CO2 is one of society’s most pressing goals.
The blue carbon solution:
One of the most promising new ideas to reduce atmospheric CO2 and limit global climate change is to do so by conserving mangroves, sea-grasses and salt marsh grasses. Such coastal vegetation, dubbed “blue carbon”, sequesters carbon far more effectively (up to 100 times faster) and more permanently than terrestrial forests. Carbon is stored in peat below coastal vegetation habitats as they accrete vertically. Because the sediment beneath these habitats is typically anoxic, organic carbon is not broken down and released by microbes. Coastal vegetation also continues to sequester carbon for thousands of years in contrast to forest, where soils can become carbon-saturated relatively quickly. Therefore, carbon offsets based on the protection and restoration of coastal vegetation could be far more cost effective than current approaches focused on trees. Furthermore, there would be enormous ad-on benefits to fisheries, tourism and in limiting coastal erosion from the conservation of blue carbon.
You can see all the organic rich sediment that gets accumulated in the mangrove roots as the forest accretes vertically. This makes mangrove forests highly effective at capturing and storing carbon emitted into the atmosphere by humans. However, when mangrove forests are destroyed for development, vast amounts of carbon is released, intensifying global climate change.
Mangroves, tidal marshes and sea-grasses are critical along the world’s coasts, supporting coastal water quality, healthy fisheries, and coastal protection against floods and storms. For example, mangroves are estimated to be worth at least US$1.6 billion each year in ecosystem services that support coastal livelihoods and human populations around the world*.
GREEN IS BLUE
by James Hutchison
My colleagues and I have just worked out how much carbon there is in the world’s mangrove forests, give or take a bit. And we mapped it. And here’s why these findings are tremendously important.
They quantify what some of us in marine conservation have been saying for a decade or more: that mangrove forests are among the most carbon rich habitats on the planet. That, although they occupy just a fraction of the world’s surface, they pack a punch. Anyone concerned about preserving nature’s value — carbon sequestration and all the other benefits mangroves provide us — needs to think hard about this.
Because on average, mangroves have double the living bio mass of tropical forests overall. This means that if you want to slow carbon emissions, one of the first places you could look would be in the mangroves. Stop an acre of loss here, and you will achieve a much bigger win than in many other areas.
As we make our increasingly bold statements about the importance of mangrove biomass — or indeed around any ecosystem services — it is so important that we have the numbers to back up our claims. Until this paper, the best we could in most places was provide a global average number. “A typical mangrove has 152 tonnes of aboveground biomass per hectare,” we might say.
That doesn’t sound at all convincing whether you are standing at the foot of canopy giant in Berau, Indonesia, or indeed on the margins of straggly community of mangrove shrubs in the desert margins of the Middle East. To do this new paper, we stood on the shoulders of hundreds of others who have sweated and toiled in the tropical heat of the mangroves, doing the real work of assessing biomass. We took numbers from 95 studies around the world and built a computer model around the climatic factors that help to drive the variability in biomass from place to place.
Mangroves in Berau, Indonesia. These are being rapidly converted to aquaculture ponds. Photo credit: Mark Spalding’
It’s a model, of course, and only captures part of reality, but it’s a huge advance. We need this sort of work — both the hard data from the field scientists and the verifiable models of what’s going on. It means so much more than average numbers. Without it, all our platitudes and pleadings about the value of nature run the risk of sounding hollow.
The map shows the real hotspots for mangrove biomass – the countries of the Coral Triangle lead the way, but the overlap with coral reefs isn’t always neat – it’s the wet muddy coasts of Sumatra, Borneo, and New Guinea that have the very high biomass. So too does an extraordinary stretch of coastline in on the Pacific coast of Columbia and Northern Ecuador.
In all these places mangroves are truly breathtaking – gigantic trees with canopies reaching well over 30m high. These are found on wide, still growing deltas where they hold together sediments and add vast amounts of organic nutrients to the soils and the surrounding waters.
When it comes to soils, we’re still struggling with the models a bit, but the story is equally compelling. Most mangrove forests lay down peat — thick, heavy layers of carbon-rich soil that stays waterlogged and doesn’t rot. There are other important peat forests worldwide, but the microbial processes in those peat forests give off pretty substantial amounts of methane, which is a greenhouse gas in its own right. The saline soils of the mangroves generally prevent this methane production. That gives us a huge extra carbon store in the soil.
But it’s not just a store. Mangroves are celebrated as one of the most productive ecosystems on the planet, and it is believed that about 10% of what they produce also gets sequestered away in the soil. That word “sequestered” should be music to our ears. In other words, mangroves are natural carbon-scrubbers, taking CO2 out of the atmosphere and packing it away, for millennia or more, in their rich soils.
So if you had a dollar to invest in carbon futures, my strongest advice of all would be to invest in preventing mangrove loss, or even restoration. There’s no magic cure to the challenges of global change – warming, rising seas, worsening storms and ocean acidification – we’ll only ever get there through a combination of interventions. Mangroves aren’t sufficiently widespread to tip the scales, but they give a greater return on investment than many other mitigation efforts. On a unit area basis, it would be hard to think of a more important ecosystem. And that’s before you even start to add up the value of mangroves for fisheries, timber, tourism, water purification, coastal protection and so on.
This work was supervised by Dr Mark Spalding. The lead author, James Hutchison, is a researcher at the University of Cambridge now working with TNC on mangrove fisheries, and the other co-authors were other Cambridge conservation scientists: Andrea Manica, Ruth Swetnam (now at University of Staffordshire) and Andrew Balmford.
LIFE IN THE HIGH SEAS in perspective of Thor Heyerdahl’s legacy
A new study published 5 June 2014 has revealed the extent to which life in the high seas is mitigating climate change, taking up a staggering 500 million tonnes of carbon per year by storing one-and-a half billion tonnes of carbon dioxide away from the atmosphere.
Filling one of the gaps in knowledge identified by the last Intergovernmental Panel on Climate Change (IPCC) (the role of the deep ocean in carbon cycling), The High Seas And Us: Understanding The Value Of High Seas Ecosystems is the first study to assess the ecosystem services of the high seas and place an economic value on them.
The study, commissioned by the Global Ocean Commission, identifies 15 ecosystem services of direct value to humans ranging from ‘provisioning’ services such as genetic resources and raw materials, ‘regulating’ such as air purification and biological control, to ‘habitat’ services such as life cycle maintenance and gene pool protection.
The Global Ocean Commission commissioned the study to help inform its inquiry into the role of the high seas in the wider health of the ocean and the relative value of the many services provided. Co-chair of the Commission Trevor Manuel said: “This study makes that which used to be out of sight/out of mind visible and we can now more obviously see and assess what we stand to lose if we do not take measures to protect the high seas and govern them effectively to preserve vital ecosystem services. This new information has informed the Commission and on 24 June we will be releasing a report and proposals for action to reverse ocean decline and restore health”.
Describing the major ways in which the ocean stores and fixes carbon away from the atmosphere, the study calculated an economic value for the role of high seas carbon sequestration as between US$74 and US$222 billion annually.
from one of the beneficiaries of Worldview’s project in Myanmar.
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- Mangroves mitigating 3-5 times more CO2 than rainforest trees
- Protecting lives and properties from extreme weather
- Increasing sea food production with up to 50%
- Filtering and cleaning water
- Providing cooling effect and other vital eco services for life on Earth
- Helping disadvantaged in vulnerable coastal communities with sustainable development to overcome poverty
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Mangrove tree(s) in Thor Heyerdahl Climate Park in Myanmar mitigating1 ton per tree documented in the soil and in the biomass.