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Wenzhou’s Annual Mangrove Eco. Value: Over $ 5 Mil
Date:2022-05-23 11:10:55 Source:Wenzhou·China Fonts:[ Large Medium Small ]

Mangrove forests on Shupaisha Island in Longwan District of Wenzhou

By the end of 2021, the mangrove planting areas in Wenzhou had reached 363 hectares (equivalent to about 508 standard football fields), accounting for 75% of the total mangrove areas in Zhejiang Province, according to news from the Mangrove Protection and Development Work Conference held in Wenzhou on May 10. Next, Wenzhou will guide qualified mangrove areas to gradually develop carbon sink trading projects to establish a blue carbon sink fund by attracting social capitals so as to contribute to carbon neutralization.

Foreign research data show that the ecological value of a hectare of mangroves growing in swamps is USD 140,00 a year. According to the calculation, local‘ mangroves contribute USD 5.082 million to the city’s annual ecological value.

Wenzhou boasts a 60-year history of mangrove afforestation

Since introducing mangroves on Ximen Island in Yueqing in 1957, Wenzhou has boasted a 60-year history of mangrove afforestation. Among them, Ximen island is recognized as China’s northern boundary of mangrove growth, and Longgang Wetland Park is the area with the best growing mangroves in Wenzhou. A series of iconic mangrove planting areas have emerged in the city, such as Emerald Shupaisha Wetland by the Oujiang River, Niyu Island with a Large Wetland, and Green Xinmeizhou Mangrove Wetland Park in Longgang.

In 2014, Wenzhou began to implement a mangrove forestation project on Longwan District’s Shupaisha Island at the estuary of the Oujiang River. At present, the mangroves, mainly Kandelia candel, cover an area of over 10,00 mu. The crisscross mangrove roots protect the tideland, purify the water, and create treasured habitats for shallow sea fish and molluscs food-foraging and breeding. According to a biodiversity investigation in the mangrove-planting areas along the Oujiang River, once missing river eels, river crabs, river crucian carps and other migratory fish have reappeared there.

Mangrove forests on Niyu Island in Dongtou District are also located at the estuary of the Oujiang River. More than 400 mu of mangroves were planted on the island in 2018, and their tree species is Kandelia candel. After the trees were planted, shellfish, fish, shrimps, crabs and other marine organisms began to multiply in the tideland of the region, enriching bird food resources and attracting many migratory birds to inhabit. It is planned to build a 3000-mu marine wetland park, featuring mangrove forest planting, migratory bird observation and ecological breeding.

The Provincial Xinmeizhou Mangrove Wetland Park in Longgang City (county-level) covers a mangrove planting area of about 300 mu. According to the plan, the wetland park, positioned as a "maritime forest and migratory bird paradise", will be built into a well-known eco-tourism leisure destination, featuring mangrove forests, waterfowl and coastal scenery.

Mangrove forests growing in Wenzhou are drought-resistant

The species of mangrove forests in Wenzhou is mainly Kandelia candel and a small amount of Aegiceras corniculatum. Kandelia candel is the most drought-resistant among the mangrove species. It absorbs seawater and discharges saline substances outside of the plant through its leaves, so that it will not "die of thirst" even if it grows in saline-alkali areas. Therefore, a little of white salt can often be found on both sides of Kandelia candel leaves. At present, the Zhejiang Academy of Agricultural Sciences Subtropical Crop Research Institute has selected four kinds of mangrove plants suitable for growing in our province, including the most cold-resistant variety of Kandelia candel, "Longgang Kandelia candel mother tree seed", which can withstand - 6 ℃. Aegiceras corniculatum, low temperature-resistant, can be widely planted but it is not as cold-resistant as Kandelia candel. Aegiceras’ fruit is shaped like a goat horn, so it is commonly known as “sheep horn tree” in some places.

"...Why don’t mangroves look red but green (as the first character in its Chinese name is called “hong” (red) ),” a colleague of mine asked. I answered that “hong” is not named after mangroves’ leave colour, but its bark, which oxidizes into red by encountering air as it is rich in tannic acid. Therefore, the plant growing in groups is called “hong shulin”(red forests) in Chinese.

Providing spaces for villagers’ fishing on tideland upon implementing mangrove restoration there

At Yanpu Bay in Cangnan County, located in the southernmost part of Zhejiang Province, the tideland ecological environment was seriously degraded ten years ago.  In 2015, Shui Bainian, a Professor of Zhejiang Ocean University Fisheries College planted 10 mu of mangroves at the Bay. Gradually, green crabs, witch-eels and other organisms that had disappeared for many years emerged under the 10 mu mangrove forests. In 2016, 750 mu of mangroves were planted along Yanpu Bay in Cangnan County. According to the Municipal Natural Resources and Planning Bureau, the three-year follow-up observation along Yanpu Bay found that the number of marine organisms in the mangrove-planted areas increased to 358 species, including 147 species of phytoplankton, 125 species of zooplankton and 87 species of benthos. In addition, more than 30 species of national protected birds above class II migrate through the bay for supplies.

In recent years, some villagers living along the Bay have increased their income by catching green crabs, witch-eels and rag worms every day. Professor Shui Bainian told them that in the future, these mangroves will be the source for them to get rich.

On December 6 last year, some citizens called a leader of the Municipal Natural Resources and Planning Bureau, saying they were worried that the current mangrove restoration implemented on the tideland would affect villagers’ catching sea products there, and thus their income. The leader told them on the phone that in planning mangrove planting, the agency has paid attention to spatial layout, leaving necessary waterways, ditches, mudflats, aquaculture ponds, etc., which generally accounts for 40% of the tideland. Therefore, the mangrove restoration plan not only provides a foraging and living environment for benthos and birds, but also leaves spaces for the villagers’ fishing.

"Mangrove ecological restoration does not mean to plant as densely as possible, but  to reasonably retain some tidal ditches and mudflats to ensure the needs of seawater exchange, bird and benthos habitat so as to maintain biodiversity," some experts said.

Establishing a standard system for the carbon sink assessment of artificial mangroves

The Wenzhou mangrove protection and development work conference strongly proposed to explore blue carbon demonstration, and with focus laid on green and low-carbon, carbon sequestration, and carbon negative emission technologies, to strengthen innovation carriers, deepen theoretical research, and provide solutions for the blue carbon accounting, monitoring, evaluation and trading of mangrove forests.

The ocean stores more than 90% of the earth's carbon dioxide. Blue carbon generally refers to the organic carbon fixed in seagrass beds, mangroves, salt marshes and coastal ecosystems. The mangrove tree canopy, with the strongest carbon absorption capacity, can absorb 11.79 grams of carbon per square meter per day. The mangrove ecosystem has become an important contributor to the blue carbon sink in the coastal zones.

Last June, the signing ceremony of carbon emissions reduction transfer agreement of the Guangdong Zhanjiang Mangrove Forestation Project was held in Qingdao of Shandong Province, marking the successful transaction of China's first blue carbon project. At the ceremony, the Beijing Entrepreneur Environmental Protection Fund purchased 5,880 tons of carbon dioxide emissions reduction in the transaction for the first time to neutralize the carbon emissions not in compliance with environmental protection requirements. All of income from the project transaction has been used to maintain the ecological restoration effects in the project areas, which benefited the surrounding communities.

Next, Wenzhou will establish an assessment model of carbon reserve and carbon sink capacity of the mangrove ecosystem, and an assessment standard system of artificial mangrove carbon sink in the northern edge of China. And an all-round sky-ground dynamic monitoring network of the mangroves will be built in Yueqing Bay, forming a mangrove carbon sink income account and a map of its distribution by three-dimensional, real-time and intelligent sensing means. At the Wenzhou mangrove protection and development work conference, the Municipal Natural Resources and Planning Bureau said that it would guide qualified mangrove-planted areas to gradually develop carbon sink trading projects, and establish a blue carbon fund by attracting social funds for Wenzhou to contribute to carbon neutralization.