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Nestled deep within one of the many bays of the Pearl River delta, a rare patch of mangroves can be found hidden between the towering skyscrapers on the Hong Kong – Shenzhen border. Egrets laze in the sun as small crabs scuttle at their feet, a mountainous skyline of construction cranes looming behind them.

Mangroves are small trees that grow along the coastlines of more than 100 countries in tropical and subtropical regions. They were once widespread on the Pearl River delta and around the inlets and islands of the neighbouring Hong Kong Special Administrative Region (SAR). Now there are only about 60 small patches remaining in Hong Kong – the largest is at Mai Po, at the head of Deep Bay (also known as Shenzhen Bay).

Protected by the Mai Po Nature Reserve, this mangrove forest and the surrounding mudflats has been designated as a Wetland of International Importance under the Ramsar Convention since 1995. It is part of a Hong Kong success story, albeit a limited one. After years of degradation, a recent survey conducted by Dr Stefano Cannicci from Hong Kong University’s Integrated Mangrove Ecology Lab found that mangroves are now making a recovery in the region.

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hong kong geopark
A single mangrove colonises the muddy edges of Hong Kong’s Kam Tin River. A new channel for the river was constructed along Nam Sang Wai in 1997. To compensate for the disruption this caused to the area’s wetlands, and to strengthen the riverbanks, species of mangrove were planted along the channel. (Image: Katherine Cheng / China Dialogue)

This goes against the general trend. Over the past 50 years, 50% of the world’s mangroves have been lost. This is due to a combination of factors, including coastal reclamation, urbanisation, unsustainable aquaculture practices and pollution.

A decade ago, the rate of loss was between 1% and 2% every year. Things have improved slightly since then – the rate is now between 0.3% and 0.6% a year – thanks to stronger recognition of the ecological benefits of mangroves and expanded management and protection. But Associate Professor Daniel Friess from the National University of Singapore cautions against being overly optimistic, telling Science Daily that “conservation gains are not evenly spread, nor guaranteed in the future”.

This caution should apply to Hong Kong as well. With space limited, urban development looms ever on the horizon. This is clearly in evidence in Starfish Bay in the New Territories, where a new housing development towers over the beach. Long-time resident Mr So is only too aware of the issues: “There’s too much pollution, and look at all these new buildings that have been built nearby. It’s changed so much.”

man working hong kong
Mr So untangles a fishing net on Starfish Bay beach. Fish haven’t been easy to catch since the new tower blocks behind him were built. (Image: Katherine Cheng / China Dialogue)

The loss of mangroves means more than just the loss of another species of plant. Walking through the Mai Po Nature Reserve in Hong Kong at low tide, it’s clear how important this ecosystem is. The tangled, gnarly roots are teeming with life, a haven between fish ponds and exposed mudflats.

But the benefits of mangrove forests go much wider. As Eddie Leung, assistant manager of WWF’s Mai Po Habitat and Infrastructure programme, explains, when seen as a nature-based solution, the ecosystem “addresses coastal erosion, prevents typhoon damage, provides a rich nursery for biodiversity, and more recently, is known for storing carbon”. For people who live in low-lying areas, this means the trees not only help protect their homes from flooding, but also provide a source of income through the fish stocks they nurture.

To conserve mangroves, protected areas and restoration projects are vital. But for mangroves in Hong Kong to continue to recover, and for these coastal forests to start making a come-back elsewhere – including on the Chinese mainland – best practice needs to be followed. Reserves need to be properly monitored and policed. And planting should only occur in areas suitable for mangroves, using only suitable local species. To this end, the exchange of scientific knowledge is key – a cooperation established in 2012 between the Mai Po Nature Reserve and the Shenzhen Futian Mangrove Ecological Park is a good example of this.

What’s happening in Hong Kong shows there is hope for mangroves. But much more needs to be done if we want to prevent this vital coastal ecosystem from disappearing by the end of the century.

tai o fishing village
A floating fish farm in Three Fathoms Cove, home to one of the few remaining areas of mangroves in Hong Kong. If practised sustainably, aquaculture can benefit from the ecosystem services mangroves provide. A richly biodiverse habitat, these intertidal forests offer a safe haven for fish to breed and raise their young, and also help clean the water of pollutants. (Image: Katherine Cheng / China Dialogue)
hong kong housing tower complex
Not far from Three Fathoms Cove at Starfish Bay, a newly built housing complex towers over the beach. At high tide, the water reaches the thin strip of mangroves providing a buffer between the beach and the buildings. Originally named after its rich biodiversity, starfish are no longer easy to find in the bay due to rapid urban development. (Image: Katherine Cheng / China Dialogue)
lai chi wo hong kong mangroves
Directly north of Three Fathoms Cove at Lai Chi Wo, a remote part of the Plover Cove Country Park, a patch of unprotected mangroves thrives in mudflats, seen here exposed at low tide. Hong Kong University researcher Brian Morton has described this patch as “the most intact mangrove in all of China”, recommending it be protected as a World Heritage Site. (Image: Katherine Cheng / China Dialogue)
woman working tai o
This elderly resident of Tai O, a fishing village on the western side of Hong Kong on Lantau island, sells traditional salted fish for a living. A decline in the number of tourists over the past year due to Covid-19 means she’s only able to sell about a third of what she used to on a good day. “But I have enough to eat,” she says. Fishing around Tai O benefitted greatly when a new patch of mangroves was planted on abandoned salt pans next to the village between 2005 and 2007. (Image: Katherine Cheng / China Dialogue)
tai o stilt houses
With its stilt houses and extensive waterways, Tai O is often referred to as the Venice of Hong Kong. The village’s 2,300 residents have, in the past, had to flee their homes to escape flooding during typhoon season. The Yim Tin mangrove forest was planted next to the village to help prevent coastal erosion, part of efforts to address this problem of flooding. (Image: Katherine Cheng / China Dialogue)
mangroves hong kong
Part of a project to compensate for mangroves lost during the construction of Hong Kong’s international airport on the northern side of Lantau island, the forest was planted in 2005-2007, and has brought many benefits to the village of Tai O. (Image: Katherine Cheng / China Dialogue)
shrimp pools hong kong
“Gei wai” shrimp ponds were introduced to Hong Kong in the 1940s by migrants from mainland China. A traditional aquaculture practice, the ponds were constructed by digging out the mud around stands of mangroves and creating embankments to keep the water in. Gates on the seaward side of the ponds allowed for the regular inflow and outflow of tidal water. The mangroves were kept to help harbour baby shrimp until they were ready to harvest. The Mai Po reserve is home to Hong Kong’s last remaining gei wai ponds – they are no longer in use, but are maintained by the reserve for their historical importance. (Image: Katherine Cheng / China Dialogue)
hong kong mangroves
Mangroves are highly tolerant to salt, using different mechanisms to extract the fresh water they need from the seawater they live in. Their complex root systems are also adept at binding the sediment brought in by the rising tide. (Image: Katherine Cheng / China Dialogue)
shenzhen mangroves
Across the Mai Po mudflats, the high-rise buildings of Shenzhen are a hard-to-miss reminder of urban spread along this coastline. A less visible threat to the Mai Po mangroves are invasive species. The fast-growing Mangrove Apple (Sonneratia caseolaris) is a non-local species that was originally planted in the Futian Nature Reserve on the Shenzhen side of Deep Bay as a quick way to restore the mangrove forests there. The species has since invaded the Mai Po reserve, where regular clearance efforts are needed to prevent it overtaking native mangroves. To address the issue, Futian and Mai Po have also formed a collaboration, holding regular workshops and exchanging data. (Image: Katherine Cheng / China Dialogue).

This article was originally published on China Dialogue, written by Katherine Cheng, and is republished here as part of an editorial agreement with Earth.Org.

Featured image by: Flickr

A court in Brazil has blocked a move by the government to revoke important regulations protecting the country’s vital tropical mangroves. The decision comes just a day after Brazil’s National Environment Council, known as Conama, voted to overturn the protection measures that defined the mangroves as “permanent preservation areas” and prohibited commercial development projects.

Federal judge Maria Amelia Almeida Senos de Carvalho overturned the decision on September 29, saying the repeal violated the constitutional right to an ecologically balanced environment. She said that the move would cause “irretrievable damage to the environment.”

Environment Minister Ricardo Salles defended the move to CNN Brasil, saying that the changes provided greater “balance” to protect the environment. He says, “this government is concerned with the environment, with people and with sustainable economic development. You can’t create legislation that is so excessive that it asphyxiates the economic sector completely.”

Mangroves are vitally important ecosystems in the fight against the climate crisis as they are some of the world’s most effective carbon sinks, capturing more than half of the world’s biological carbon. Additionally, their large root systems protect coastal areas from erosion and besides providing habitats to sea birds, they are called “nursery habitats” because they provide shelter to young fish, crabs and shrimp.

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Greenpeace said that removing the protections for mangroves was “calculated environmental destruction” in Brazil.

The government of Brazil has been widely criticised for its disregard for environmental regulations. In May, a video of a governmental meeting showed Salles, saying that the government should take advantage of the media’s focus on the COVID-19 pandemic to loosen the environmental restrictions. He said, “There is a need to have an effort on our side here, while we are at this moment of tranquility in terms of press coverage, because it only talks about COVID, and let the cattle herd run and change all the rules and simplifying standards.” He later claimed that the statements were aimed at reducing bureaucracy.

President Jair Bolsonaro has long rejected criticism of his government’s environmental policy, even as data from his own agency shows that deforestation in the Amazon and the Pantanal has increased. In 2019, Brazil’s National Institute for Space Research (INPE) counted 126 089 fires in the Amazon- a rise of nearly 40% from the year before.

By mid-September, the INPE reported 16 119 heat spots in Pantanal, the most since 1998, when records started. Bolsonaro accused foreigners of a “brutal disinformation campaign” in a pre-recorded address to UN members last week.

An international team of 22 researchers led by National University of Singapore (NUS) has found that the global loss rate of mangrove forests is less alarming than what has been previously suggested, a welcome development for one of the most valuable ecosystems on the planet. 

According to Dr. Daniel A. Friess of NUS, loss rates of mangrove forests were estimated at 1% to 3% per year during the late 20th century. Now, the loss rate has dropped to 0.3% to 0.6%. This drastic drop is due to successful mangrove conservation efforts around the globe.

Mangroves are trees or shrubs that grow along the coastlines of more than 100 countries in subtropical or tropical regions. They provide two different types of habitats for a bustling variety of fauna: underwater roots and tree and shrub foliage above ground. Mangrove roots, in particular, are home to a diversity of invertebrates (particularly crabs, snails and worms) and fish. 

Mangroves also possess root systems that reduce water pollution by absorbing inorganic substances. Notably, mangroves are excellent at storing carbon from the atmosphere, making them great air purifiers.

Mangrove forests offer many benefits to people, including protection from coastal erosion and storm damage. They also provide people with products such as fuelwood, construction materials and fisheries resources, since mangroves act as nurseries for many coastal fish. 

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According to Dr. Stefano Cannicci’s research, Hong Kong’s mangroves in particular harbour “eight species of trees, fifty-three species of crabs and forty-two species of snails, which is more than what is currently known for the mangrove forests of the whole African continent.” 

The team determined that the reduction in mangrove global loss rates is the product of improved monitoring and data access, changing industrial practices, expanded management and protection, increased focus on rehabilitation and stronger recognition of the ecosystem services provided by mangroves.

In Hong Kong, for instance, much has been done in the past 20 years to conserve mangrove forests. The government of Hong Kong has attempted to preserve mangroves by designating marine parks and reserves to protect marine habitats throughout Hong Kong. The Mai Po Inner Deep Bay Ramsar and the surrounding Inner Deep Bay wetlands is one of these reserves. Home to tens of thousands of migratory waterbirds, the Mai Po Nature Reserve and the surrounding wetlands have been recognised as a Wetland of International Importance under the Ramsar Convention since 1995. Mangroves in Hong Kong represent the largest remaining mangrove patch within the Pearl River Delta. 

However, mangroves continue to be threatened by aquaculture, agriculture and urban development. Southeast Asia is a hotspot for mangrove deforestation as mangroves are cut down to make space for aquaculture ponds, cleared for rice paddy cultivation and reclaimed for industrial development. 

“However, despite recent mangrove conservation successes, tempered optimism is necessary, as conservation gains are not evenly spread, nor guaranteed into the future,” cautions Dr. Friess. Countries such as Myanmar, Indonesia and Malaysia continue to show rates of loss that are substantially above the global average, due to the rapid expansion of rice cultivation in Myanmar and the rise of oil palm plantations in Malaysia and Indonesia. This is why conservationists need to make sure that conserved and rehabilitated mangrove systems are ecologically functional and adaptable to challenges such as sea-level rise, deforestation and damming. 

Mangrove forests won’t survive sea-level rise and will disappear by 2050 if greenhouse gas emissions aren’t reduced, according to a new study. 

How Does Sea-Level Rise Affect Mangrove Trees?

The study, published in the journal Science, used sediment data from the last 10 000 years to estimate the chances of mangrove survival based on rates of sea-level rise. It examined sea-level rise across 78 locations and explored how mangroves responded as the rate of sea-level rise slowed from more than 10mm yearly 10 000 years ago (as a result of glacial ice melt) to nearly stable conditions 4 000 years later. The storage of carbon as mangrove forests expanded during that period means that these ecosystems are important carbon sinks.

It found that when rates exceeded 6mm per year, similar to estimates under high-emissions scenarios for 2050, mangroves were likely to stop keeping pace with the rising water levels. Instead, mangroves are more likely to survive when sea-level rise is less than 5mm per year- which is projected for low-emissions scenarios this century. 

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Erica Ashe, a postdoctoral scientist at Rutgers University- New Brunswick and co-author of the study, says, “Under high-emissions scenarios, rates of sea-level rise on many tropical coastlines will exceed 7mm per year, the rate at which we concluded there’s a 6.2% probability mangroves can sustain growth. The loss of these mangrove ecosystems could result in increased carbon dioxide in the atmosphere and fewer vital buffers against storm surges in the long run.

Mangrove trees and forests are valuable coastal ecosystems found in Florida and Bangladesh, as well as other warm climates that store large amounts of carbon dioxide, reduce erosion from storm surges, currents, waves and tides, help protect coastlines and provide habitat for fish and other species. There are about 80 species of mangrove forests and they line nearly 3 000 km of shoreline. 

They naturally move inland if they can’t build vertically, but human development along coastlines hinder this movement. These areas are also deforested to make room for shrimp farms and other forms of aquaculture, as well as for their wood. They need freshwater to survive and can die when dams and other upstream developments stem the flow of rivers. 

Studies show that, pound for pound, mangroves can sequester four times more carbon than rainforests can. Most of this carbon is stored in the soil beneath the trees. In 2000, mangrove soil held around 6.4 billion metric tons of carbon. Between 2000 and 2015, up to 122 million tons of this carbon was released due to mangrove forest loss. 

Their monetary value is equally as important as their carbon-sequestering abilities. Researchers estimate the monetary value of the ecosystem services provided by these trees at US$194 000 per hectare annually. Multiplied by their global extent, the world’s remaining mangroves provide around $2.7 trillion in services every year.

The rate of sea-level rise has doubled from 1.8mm per year over the 20th century to 3.4mm per year in recent years. The scientists stress the importance of mitigating this rapid sea-level rise and ensuring that coastal adaptation measures allow mangrove forests to expand across coastal lowlands and not disappear before our eyes.

Featured image by: James St. John

As cities are forced to adapt to the challenges of the climate crisis, communities are moving away from traditional engineered responses to using ecosystem-based adaptation services.

Communities worldwide have become more vulnerable to extreme weather conditions and natural disasters caused by climate change. The Global Climate Risk Index 2020 reported that globally, 495 000 people have died as a direct result of more than 12 000 extreme weather events. The index also reported that the world economy has lost US$ 3.54 trillion (in purchasing power parities) from 1999-2018 due to extreme weather conditions. In the past, engineered solutions have been implemented to mitigate the effects of the climate crisis. However, local communities are now adapting through natural solutions called ecosystem-based adaptation (EbA). 

Ecosystem-based adaptation services involve using natural services provided by the local ecosystem to help minimise the impacts of climate change on local inhabitants and biodiversity. The approach aims to provide long-term ecological and socio-economic benefits to local residents. A briefing released by the UN Environment Programme (UNEP) shows that EbAs are economically viable solutions as they can be more cost-beneficial than engineered solutions. Currently, EbAs are being implemented in a range of ecosystems, including mountains, coasts, wetlands, drylands and urban cities.

Examples of Ecosystem-Based Services:

Madagascar’s Blue Forest

For decades, mangrove forests in Madagascar have undergone high rates of deforestation for urban development, agricultural purposes and wood use. Globally, mangroves are declining at a rate of 1-2% annually, however, in comparison to previous decades, the rate of mangrove loss is in decline. This could suggest growth in awareness among communities of the importance of mangroves. Mangroves are sinks which are able to sequester more carbon than other kinds of forest systems and at times up to 3-5% more carbon than upland tropical forests. Studies suggest that mangroves also have the ability to adapt to three millimetres of rising sea levels annually. Because of their resilience, mangroves are now being used as a tool in the fight against the climate crisis.

Madagascar has restored 1 200 hectares of mangroves to adapt to rising sea levels and to facilitate large amounts of carbon sequestration. The country implemented a combination of engineered and ecosystem-based approaches. To combat rising sea levels, along with the restoration of the mangrove forest, a 1 km sea wall has been built as a defence in the cities of Manakara and Toamasina to reduce coastal erosion. The initiative of combining approaches has resulted in a more resilient coast line.

The Cloud Forest of Xalapa

Xalapa, a city situated in the foothills of Mexico, has also embraced EbA, in partnership with the UNEP. The city is surrounded by a cloud forest, an indigenous rainforest located in the mountainous regions. The forest plays a major role in carbon sequestration and in providing water to the inhabitants of Xalapa, controlling the water flow. Trees also reduce the frequency of landslides and erosion through soil retention, which in turn prevents flooding and droughts.

Due to deforestation, the forest has been reduced to one percent of its original size. Locals are threatened by the climate crisis as changing temperatures and irregular rainfall has caused landslides in the urban settlements nearby. Reports suggest that by 2039, the forest could experience a temperature rise of 1.8 which will be detrimental to the ecosystem, as well as to local farmers. To minimise the damage caused by these landslides, the city is working to restore the cloud forest and use the trees as an ecosystem-based adaptation tool for. Restoration efforts include planting montane forest species on the mountain slopes, planting native riparian plants along streams to conserve the soil, and building ditches and berms for soil retention and improved water infiltration.

Urban Wetlands of Laos

Laos has been frequently impacted by urban flooding as a result of the climate crisis, which has been detrimental for the economy; the total damages and losses caused by flooding in 2018 cost the economy an estimated US$371 million, exacerbating poverty and placing further pressure on resources. Laos clearly needs a long-term solution should flooding become the norm for the country (as it appears to be becoming) and in mid-November, the UNEP announced a project in the cities of Vientiane, Paksan, Savannakhet and Pakse, that will help 10% of the country’s population become resilient to climate change.

The project takes an alternative route from the traditional urban management approach implemented through infrastructure. Instead, the goal is to restore 1 500 hectares of urban wetland and stream ecosystems; these ecosystems play a major role in regulating water flow and filtration and restoring them will reduce the flooding that has been plaguing the country. The Deputy Director-General of the Department of Climate Change at the Ministry of Natural Resources and Environment of Laos, Syamphone Sengchandala, stressed the importance of the project, saying: “This project offers hope for the future by recognising that nature provides some of our greatest defences against extreme weather. The question is whether we can learn to protect these natural services, and this project is a major step forward.”

As the pressure of the climate crisis mounts, communities around the globe are trying to develop new methods to become resilient. Ecosystem-based adaptations are approaches that have shown to be effective in mitigating the effects of the climate crisis, and allow communities to flourish and maintain their livelihoods despite the difficulties posed by it.

The largest mangrove forest in the world in the Sundarbans is shrinking. A new coal power plant might wreak havoc on the already vulnerable region.

The Sundarbans: The World’s Largest Mangrove Forest 

The Sundarbans- the largest continuous mangrove forest on the planet that spans more than 10 000 sq km along the Bay of Bengal- is shrinking. Thanks to human encroachment and climate change, the forest has been losing almost 16 sq km of vegetation per year since 1991.  Earth.Org’s own analysis based on satellite imagery shows that in Bangladesh, home to the largest swath of Sundarbans mangroves, the forest has lost 442 sq km of its vegetation in the last 28 years. 71% of the forested coastline is also retreating by as much as 200 metres a year due to coastline erosion. 

Containing multiple UNESCO Natural World Heritage sites within itself, the Sundarbans forest is home to a wide variety of plant and animal species. The flora is comprised of a rich mosaic of different types of vegetation; half of all known 110 mangrove species are found within the delta. It is home to over 260 bird species, Indian otters, spotted deer, wild boar, fiddler crabs, mud crabs, three marine lizard species and five marine turtle species dwell in this impervious maze. The forest also hosts endangered species like the estuarine crocodile, Indian python and the iconic Bengal tiger. The mangrove ecosystem plays an indispensable role as breeding and nursery ground coastal fisheries in the Bay of Bengal. 

The Sundarbans is also a natural barrier that protects over 6.5 million people who live in the region from tides and cyclones. For the inhabitants of surrounding areas, the forest is an abundant source of subsistence. 

Human interference in the form of upstream agriculture, industrial shrimp farming, logging and hydrologic interventions have been gradually deteriorating the mangrove ecosystem. 

Active human encroachment is coupled with the collateral effects of the climate crisis.  The forested coastline is being rapidly overtaken by rising sea levels and storm surges. The increased salinity of the soil has made hectares of mangroves weaker and more vulnerable to retrenchment. Scientists warn that a continuing coastline retreat will trigger major mangrove disappearance within the next 50 years. 

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Earth.Org used NASA’s Landsat satellite data to generate images to analyse the changes in vegetation in Sunderbans.

A new threat 

Construction of a new cross-border coal-fired power plant is underway in the nearby town of Rampal. Despite strong opposition from UNESCO, the 1320-megawatt plant is set to start generating power by March 2021. 

Leading conservationists argue the power plant would spew thousands of tons of toxic coal ash and air pollutants, and discharge mercury-laden water at varying temperature into rivers, damaging water quality.

“Despite objections from UNESCO’s World Heritage Committee (WHC) and the International Union for the Conservation of Nature (IUCN), Bangladesh has approved more than 320 industrial projects in the area, including the massive Rampal coal-fired power plant, bypassing requirements for public participation and environmental impact assessment,” says United Nations (UN) expert John H. Knox

Preservation of Mangrove Forest in Sunderbans

The bilateral cooperation between Bangladesh and India and the Ramsar Convention had improved conservation strategies at the Sunderbans in the last decade. But experts say it is highly critical to avoid human pressure on the wetland and its resources in the future too. Both governments need to take environmental concerns into account while installing industrial projects near the mangrove forest.  

Governments should invest towards agricultural techniques that mitigate damage caused by environmental changes and by the encroaching threat of the fossil fuel industry. Traditional practices endemic to the region can adapt to periodic ecosystem disruptions, such as rising sea levels or waterlogging. An example includes a practice in Bangladesh of implementing floating cultivation systems that utilise soilless beds made from seaweed. Sustainable and regionally traditional agriculture can significantly increase the market value of commodities. If traditional and sustainable agriculture becomes the norm in the region, the value of commodities will rise and revenue from foreign markets will increase substantially. With more diversified revenue streams, the state can justify the higher cost of implementing renewable energy infrastructure rather than allowing the region to become reliant on fossil fuels.

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