Sewage ditches, garbage pools, farms... Why do scientists go there?

Eupatorium adenophorum

Water hyacinth

Mirabilis jalapa

Coral vine. Photo courtesy of Shanghai Jiaotong University Press.

In the past five years, a group of plant taxonomists have been picking up "weeds" in urban sewage ditches, garbage pools, construction waste areas, and wastelands instead of in forests, grasslands, and nature reserves. Under the scorching sun, they are sweaty and smell like homeless people, and their clothes are covered in mud... often attracting puzzled looks from people around them. They are conducting field surveys for the compilation of a special flora - "Invasive Flora of China".

Nowadays, with the acceleration of international economic and trade processes, the harm caused by alien invasive species in our country is increasing year by year, and China has become one of the countries most seriously affected by alien biological invasions.

In 2014, Ma Jinshuang was a researcher at the Shanghai Chenshan Botanical Science Research Center of the Chinese Academy of Sciences. Under his leadership, the "Flora of Alien Invasive Plants in China" project was officially launched.

Not long ago, the country's first comprehensive and systematic survey and compilation of alien invasive plants was officially completed, and its results, the first "Atlas of Alien Invasive Plants in China" (five volumes), were published by Shanghai Jiaotong University Press.

Lack of background data on invasive alien species

At the end of 2021, many parts of China were harassed by invasive plants, which attracted considerable social attention. For example, Canada goldenrod "aggressively" seized territory in Wuhan, and water hyacinth suddenly "attacked" and blocked rivers in many places in Jiangxi.

Reports of invasive plants are common. They are spread or introduced into foreign areas accidentally or intentionally through nature and human activities, and establish reproductive populations by naturalization, which in turn affects the biodiversity of the invaded areas, damages the ecological environment of the invaded areas, and causes economic impacts or losses.

According to Ma Jinshuang, the introduction of foreign plants into my country has a very long history. According to the "Tang Materia Medica" in 659 AD, castor was introduced to China from eastern Africa as a medicinal plant, and was promoted for cultivation as an oil crop in the 1950s; "Compendium of Materia Medica" (1578) recorded that Datura was introduced into my country as a medicinal plant in the late Ming Dynasty; "Yunnan Records" (1625) recorded that the single-thorn cactus native to Brazil and other places was introduced and cultivated as a flower in Yunnan; Acacia native to tropical America was introduced to Taiwan, China by the Dutch in 1645 and cultivated as an ornamental plant.

Since the 19th century, Western powers have established trading ports to expand their colonial rule and sphere of influence, and trade has been free. Explorers, missionaries, teachers, customs officers, plant collectors and botanists from many countries have come to my country to collect and study plants, which has led to a sharp increase in the number of foreign harmful plants invading China and abroad. my country's coastal cities have become the main entry points for the introduction of foreign plants.

"In the 20th century, especially after the reform and opening up, with the rapid development of my country's international trade, the risk of invasion of alien plants and quarantine pests in imported minerals, grains, seedlings and other commodities has increased dramatically. In addition, China has a diverse ecosystem, and most alien species can find suitable habitats in China. Therefore, the situation of biological invasion in my country has become more severe," said Ma Jinshuang.

"In contrast, we lack basic data on invasive alien species. Often, only species that have already caused significant ecological and economic impacts attract attention and attention, while risk prediction and prevention are not possible."

Therefore, conducting surveys and cataloging of alien invasive plants and identifying their species composition, origin, distribution pattern, introduction method, transmission pathway, and invasiveness are important foundations for preventing and controlling alien invasive plants.

It is in this context that the "Atlas of Alien Invasive Plants in China" project was officially launched. A total of 11 scientific research institutions and universities across the country participated. The project team members were divided into five major regions (East China, South China, Central China, Southwest China, and the Three Norths), and began a comprehensive survey of invasive plant species on a county basis.

The difficulty of investigation and verification has increased

In the following five years, the project team conducted field surveys and collected a large number of specimens, obtaining first-hand information on the species, distribution status and degree of damage of alien invasive plants.

"Because invasive plants are more susceptible to human interference, the field survey areas are much more complex than those for ordinary plant species surveys," explained Tang Saichun, a researcher at the Guangxi Institute of Botany, Chinese Academy of Sciences.

Under the scorching sun, the team members carried plant collection bags and walked along the streets and roadsides with one or two students. They also went to sewage ditches, garbage pools, construction waste areas, wastelands, farms, old houses, etc. to "pick up" specimens that were considered weeds by people. They smelled of sweat like homeless people, and their clothes were covered in mud... They were often mistaken for looking for "treasures" with "special" value. When they were pressing specimens under trees or on the roadside, they often attracted a lot of onlookers.

Ma Jinshuang told China Science Daily that the "Atlas of Alien Invasive Plants of China" is different from traditional flora and requires in-depth collection and verification of information on China's alien invasive plants, which is a more tedious and arduous desk work.

It includes sorting out the time and place, mode and spread pathways of invasive plants introduced into my country, and predicting areas in China where invasive plants may spread. It also explains the characteristics of invasion from three aspects: reproduction (seed set rate, germination rate, seedling growth rate, etc.), invasiveness (weight of the transmitter, structure of the transmitter, degree of association with human activities, etc.) and adaptability (climate, soil, phenotypic plasticity of the species itself, etc.), and introduces the hazards of invasive plants and prevention and control measures.

In this process, it is extremely difficult to determine the type specimens of invasive species. Since these plants are not native plants, and it is unclear in which herbarium the type materials of some species are stored, it is very difficult to find them, and it often takes several hours to complete the description of the type information of a species.

In addition, some historical specimens and early documentary information are very scarce. The project team members have to overcome various difficulties and combine various books, authoritative databases at home and abroad, flora and early plant literature records in Hong Kong, Macao and Taiwan to repeatedly verify the time and method of introduction of these plants into China for the first time, and other previously unrecorded information.

"What is even more troubling for scientists is that, in addition to alien plants that have clearly caused harm, those species that have relevant literature reports, have not been found to cause significant harm by field surveys by project team members, or whose future development trends are still unknown, should be included in the annals? If included, how should the potential risks be assessed and corresponding prevention and control measures proposed? These controversial issues need to be discussed and revised repeatedly," said Liu Quanru, professor at the School of Life Sciences of Beijing Normal University.

Take the Primulaceae as an example. This species originated in North America and Europe and later entered South America, Australia, and Taiwan. On the surface, the plant is small and not very harmful. However, Liu Quanru analyzed that as a wetland plant, it spreads quickly and is easy to break out in large numbers in a short period of time. It may invade farmland and reduce crop yields. Therefore, he still suggested that it be included in the list and proposed to strengthen investigation and monitoring.

From cognition to prevention

At present, there are 14,000 to 15,000 alien plant species in my country, of which 90% are cultivated species, about 1,000 species can survive independently in the natural environment, and more than 400 species have varying degrees of invasion risks.

The Catalogue of Invasive Alien Plants in China is divided into five volumes, covering 402 species of invasive plants from 68 families, 224 genera, and the project team collected 50,000 specimens of approximately 15,000 invasive plants, and took more than 150,000 high-definition photos of plant habitats and plant close-ups. It also recorded information on the species, abundance, and GIS of invasive plants at the county level across the country, providing the most systematic summary of invasive plants in my country at this stage.

Ma Jinshuang mentioned that during this process, the project team discovered a large number of invasive species that were reported for the first time, such as Amaranthus scabra, Amaranthus serrata, Amaranthus serrata, and Amaranthus erectus.

Clarification was given to some species that were reported to be invasive in the literature but were found in field surveys to be only in cultivation or to have occasionally escaped into the natural environment but had not yet established stable invasive populations.

Corrections were made to some species that were incorrectly identified or had their scientific names misused in previous literature, and further verification was performed on species whose origins were disputed.

With the changes in time and space, the growth and invasion of alien plants will show strong dynamic changes. Ma Jinshuang emphasized that studying alien invasive plants is a long-term task, and the current results are only a phased epitome of the plant invasion process. It is necessary to conduct more in-depth research on it in the future.

During the investigation of this project, scientists realized that the impact of alien invasive plants on the ecological environment is becoming more and more serious, but most people do not have enough understanding of their harmfulness, and relevant departments have not taken active and effective measures to deal with it.

"I hope this set of books can provide reference for scientific research, popular science, teaching, management, etc." Ma Jinshuang suggested that first of all, we must do a good job in quarantine of imported goods and commodities, and keep species with significant invasive tendencies out.

For invasive species with clear potential risks, strict control should be implemented to prevent them from escaping and they should be eliminated in a timely and scientific manner.

In addition, we should pay attention to raising public awareness of invasive species and avoid blind picking and transplanting in the wild.

China Science Daily (2022-01-14 Page 4 Culture)

Author: Hu Minqi

Editor | Zhao Lu

Typesetting | Zhihai