They are committed to the study of mangroves.

They have been out in the wild for a long time, facing unexpected dangers frequently.

Although they did not work on the first-team of mangrove restoration work, they provided data support for scientifically and rationally promoting the restoration of mangrove wetland ecosystems.

They are students in the research group of Professor LIN Guanghui, Department of Earth System Science, Tsinghua University.

This official blog introduces "The Story Behind Scientific Research of Tsinghua’s Earth System Science-The ‘Backstage Heroes’ Guarding the Mangroves”, which will take you to understand the youth story written with love and sweat in the mangroves.

In April, Hainan has already entered midsummer early, and under the scorching sun, a dozen students were wearing pants weighing more than a dozen kilograms to conduct field investigation on the beach. A dozen black mosquitoes were landing on BAI Jiankun's arms simultaneously. With hands covered in mud, he had no chance to wipe his hands, rubbing his arms with his face to drive mosquitoes away was all he could do. BAI Jiankun is a 2016 PhD student in Department of Earth System Science of Tsinghua University. At this time, he was leading his junior brothers and sisters to conduct sample investigation in mangrove forests of Hainan.

In April, 2018, it has been more than three years since BAI Jiankun went to the mangrove forest for the first time, but for GOU Ruikun, who has just entered Department of Earth System Science, his first experience of walking into the mangrove forest is still unforgettable. "I had my master's degree at Northwest A&F University. I mainly studied Pinus tabulaeformis plantations (coniferous forests) in Loess Plateau. At that time, I felt that climbing very high and steep slopes with cement piles of a permanent sample site on the back is already awfully painful. However, when I stepped into the mangrove marshland for the first time, I was still shocked to see that I had to work in such an environment for a day. I remember that I sank into the silt as soon as I stepped in it, and half of my body sank in because my feet slipped. It was difficult to pull out. The harder I pulled, the deeper it sank. I would sit into the water completely if I pull myself harder. Sea water poured into my whole water pants."

This mangrove forest that grows at the junction of land and sea has many interesting appellations. Since the bark is rich in tannins and turns red when oxidized by air, it is called the plant that is most “misnomer”; it is also known as the "maritime forest" and the "coast guard" because of its functions including carbon sequestration, water purification, wave protection, and land promotion. It has deep roots in tidal flats. It windward to the sea. It is also an important habitat for rare and endangered waterfowl, and a place where fish, shrimp, crabs, and shellfish grow and breed. According to statistic, there are about 120 million people living near mangroves in the world. The ability of mangroves to withstand tsunamis and storm surges far exceeds that of any human engineering.

Sweating among the mangrove trees, youth is just worth it

In 2017, Professor LIN Guanghui from Department of Earth System Science of Tsinghua University applied for Ministry of Science and Technology Fundamental Resources Investigation Project-Hainan Mangrove Biological Resources Investigation Project. At that time, BAI Jiankun just finished his course. As the only male student enrolled that year, he began to assist Teacher LIN to undertake this project. From November 2017 to 2019, he traveled almost all over 4000 hectares of mangrove forests in Hainan, and the collected sample data can cover almost all mangrove species in Hainan.

Speaking of the fieldwork experience, BAI Jiankun said frankly, "In fact, the most difficult thing is not collecting data, but the preliminary inspection and preparation work." In order to ensure the safety of more than 20 counterparts, every time before going out in the wild, he would go "casing" first. "I remember that I was riding a small motorcycle and looking for mangroves along the river bank. Since we had to bring equipment and various supplies, to plan the itinerary, and to find the best entry point based on the tide time." As the most experienced student in this team, such eminent job naturally fell on him. BAI Jiankun’ s junior fellow, GOU Ruikun, said, “the work of inspection is very important. First, we must know the specific distribution and environment of mangroves, and how to get deep into the mangroves, therefore, the teachers would choose the most experienced, the strongest, the most directional, and the most dexterous students to undertake this job. If there is no inspection, it is very likely that everyone would all be trapped as soon as they enter, which is troublesome and dangerous."

benthos screening in Danchang, Wenchang

Although the tide table was referenced every time before entering the mangrove, the time of rising and falling tides was not completely accurate. "Sometimes the tide hadn't receded when we arrived at the observation site, so we could only wait aside for an hour or two. If we couldn't wait, we had to forge ahead tenaciously," BAI Jiankun said, "there were other times when the tide rose high that could reach the chest, but we hadn’t got out yet. At that time, a lot of creatures started migrating. During flood tide, the water was very turbid and muddy, we couldn’t see the underwater organisms clearly."

GOU Ruikun also has a similar experience, "sometimes since our workloads were relatively large, our tasks hadn’t been completed when rising tide. Frequently, flood tide had already started when we got out, with relatively fast speed. For safety, we usually started to walk outside when the tide reached a certain level. But once, we got lost while coming out. Even the local guide couldn't find the exit. We kept walking around inside, and we drank up all the water with us. A fellow student had heatstroke, so we took turns to take care of him. The good news was that senior fellow BAI finally came in and found us and took us out of danger."

SONG Shanshan, a 2020 doctoral student, recalled that, early before going into the mangroves, she had heard that it was easy to get trapped, so she thought it would be better to walk faster. It turns out that her two legs couldn't get pulled out within a few steps, and with a stagger, her hands also lied into the mud. "I specially wore a white T-shirt, but when returning from the mangrove forest, my water pants and T-shirt were all muddy."

Asked if he had encountered any danger during fieldwork, BAI Jiankun recalled, “I encountered a snake which was several meters long. I was also stung by a red fire ant and half of my body was numb.” According to him, an inspection usually takes about two to three weeks. The expedition team is usually divided into three groups, namely the plant group, the microorganism group and the benthic organism group. After arriving, they will collect samples separately and help each other. Basically, they go in together and go back together. "Sieving the soil is a relatively heavy task. If you want to collect benthic organisms, you have to lift the soil to tidal ditches or adjacent ditches to wash, and sift benthic organisms out. This bucket of soil usually weighs tens of kilograms. We need to carry it when walking in the silt. Girls can't carry it at all," BAI Jiankun said, "our group may not be similar as other research groups. We need everyone's unity and cooperation. If someone gets stuck in accidentally, and nobody respond to the crying for help, we would have to go back and look for him..."In the view of post-doctor DING Yali, BAI Jiankun has been able to walk in the mangrove forest proficiently.

Sample investigation in Gangqi Mountain, Dongzhai, Haikou

Each time, depending on the length of time of the investigation, the expedition team not only had to carry heavy equipment, but also some food. "To be honest, there is no condition to eat inside. Everyone should bring as much water as possible when they go in. Many of the mangroves in Hainan are next to villages, and there will be lots of daily sewage. There is no way to completely clean ourselves, so we usually eat a lot in the morning, and then get cleaned and finish my work before eating."

Looking at the photos of the field trip, we found that they didn't wear gloves during many times. "Because wearing gloves is inconvenient, we simply went scooping in the mud with bare hands," BAI Jiankun said, smiling, "there are too many difficulties to overcome. We have also encountered that our collected samples were being forcibly thrown away by local residents. They think it is our investigation that made the government returned the ponds back to forest, but in fact this work has been planned many years ago."

With the efforts of all parties, mangrove restoration project has achieved some results. According to the data released by Hainan Province, during the "13th Five-Year Plan" period, Hainan Province continued to carry out special wetland protection actions, and focused on strengthening the protection and restoration of mangrove wetlands. A total of 44,000 mu of ponds were returned to wetland, of which 12,000 mu was newly constructed. Behind this, research work on mangroves is inseparable. "Under the guidance of our instructor, Professor LIN Guanghui, we have done various studies on mangroves. “Our ultimate goal is to protect it, restore it, and maintain its diverse ecosystem service functions," GOU Ruikun commented.

Persist, and eventually there will be "highlight moments"

From November 2017 to February 2021, BAI Jiankun published an online research paper titled "Mangrove diversity enhances plant biomass production and carbon storage in Hainan island, China" in the classic ecological journalFunctional Ecology. Based on field sample inspection, he reveals the factors that affect biodiversity, biomass and carbon sink relationships of mangroves located in Hainan, China, as well as factors of the geographical distribution pattern of mangrove carbon sinks. In order to come to this conclusion, he and his classmates measured the mangrove forests in Hainan with their steps, and collected huge amounts of data with sweat and bare hands. Together with the later data processing and paper writing, it lasted more than three years. "Our work, to put it more bluntly, is a bit 'thankless'. One is because it is difficult to do; the other is because there are so many factors affected. In addition, it also consumes a lot of human resources, material resources, and financial resources, with slow-coming results and plain influence. After all, compared to large terrestrial forests, mangroves are only a small piece of land."

Plant sample inspection in Bengkan, Wenchang

Even so, hisjunior fellow GOU Ruikun expressed excitement and pride at achievements of his senior fellow. "In my opinion, although the direction of my junior fellow brother is not so 'high-yield' in the current popular ecological research field, it is indeed a very important content. Because whether it is model simulation or remote sensing estimation, a large amount of support by ground and field inspection data to verify accuracy is required. Producing results is extremely hard in this work, but after the paper was published, everyone thought it was very precious. My colleagues were all very excited," GOU Ruikun said.

In DING Yali's view, BAI Jiankun has the tenacity and professionalism to engage in scientific research. "When doing scientific research, he knows what to do first and then what to next. He is a clear thinker who can endure hardship."

"In recent years, the public's attention to mangroves at home and abroad has been increasing. For example, as soon as this article by senior fellow brother BAI went online, reading volume of one day and one week ranks extremely high among the papers published in the journal. Many domestic and foreign media also reported. Therefore, I found that the research led by our teacher, Professor LIN Guanghui, is not always sitting on the "cold bench". As there are more and more research papers on mangroves or coastal blue carbon, everyone is gradually realizing that besides terrestrial forests and grassland ecosystems, there are also some very fragile blue carbon ecosystems in coastal areas that need to be protected urgently. Perhaps it is the gradual display of the research results of colleagues, which gives a lot of encouragement to our students who are in primary research stage," GOU Ruikun said.

What is gratifying is that their research conclusions have attracted the attention of government. BAI Jiankun said: "We went to Wenchang these two times and found that many fish ponds were planted with mangroves. This phenomenon can also be seen in other areas of Hainan. In addition, the conclusion mentioned in the study that ‘mangroves with high biodiversity are also strong in carbon sequestration’ also provide a reference for government’s decision-making. When restoring mangroves, government should pay more attention to mangroves with high biodiversity, which will be a key area for mangrove protection and ecological restoration in the future. In addition, mangrove ecological restoration should focus on the functioning of ecosystems and cautiously introduce fast-growing exotic species. Ecological restoration is not simply ‘greening’ or ‘planting trees’, it should focus on the functioning of mangrove ecosystems instead of pursuing restoration effects. What to grow and where to grow is more important. "

SONG Shanshan also chose mangrove-related research after enrolling. “I think this research is very meaningful for ecological restoration, so I chose it,” SONG Shanshan said.

For DiING Yali, engaging in ecological research stems from her love for nature. Whether facing a karst with complex terrain, or being in the open Mexican grassland, or the winding mangrove root system that appears after low tide, they are all so original and pure.

Indeed, ardent love can resist all difficulties.

Text: WANG Jiayin

Image: BAI Jiankun

Review: WU Haiping