Sri Lankan medicinal plants under threat due to climate change

This article is helpful because of its content which,

• Calls for reorienting conservation strategies.
•  Provides insight to policymakers for future conservation.
• Creates awareness of the real impact of climate change on medicinal plants in Sri Lanka.  

Medicinal plants are diverse, including annuals, biennials, perennials, etc. Typically, all parts of medicinal plants are utilized for different purposes. They grow in various habitats and all climatic regions. About 50,000-70,000 plant species are used worldwide in traditional and modern medicines.  

Four traditional medicine systems exist in Sri Lanka: Ayurveda, Siddha, Unani, and Deshiya Chikitsa. The Ayurveda and Deshiya Chikitsa medicines are mainly prepared using plants and herbs. The former uses about 2000 species, the latter about 500. The plants are used individually or as mixtures.

Sri Lanka imported $815 million worth of western medicine and pharmaceutical products in 2021. It is evident how dependent Sri Lankans are on western medicine. Although, with the current economic crisis, the country invested only about $25 million in medicine this year. Hence, there is a rise in the need to improve traditional medicine and maintain medicinal plants in the country. However, climate change is the main stumbling block.  More can be read here, Archived.

Climate change affects the germination of medicinal plants!

A research study published in the journal Global Ecology and Biogeography used data from seed germination experiments compiled by the Royal Botanic Gardens Kew to calculate germination tolerance. Characteristics such as maximum, minimum, and optimum temperature for over 1,300 plant species spanning every continent except Antarctica were recorded. They found that many species, particularly those in the tropics, already live outside their optima and likely suffer reduced germination rates. Over 20% of plant species in the tropics may face temperatures higher than their maximum germination temperature. Over half of the tropical species may have reduced rates of germination. Read the research article here.

Effects on plant life cycles due to climate change

Research published in the world Ayurveda congress states that there are pieces of evidence that climate change is causing noticeable effects on life cycles and the distribution of plant species.

Generally, when plants are stressed, secondary metabolite production may increase because growth is often inhibited. The plants allocate more carbon to photosynthesis, and plant growth is instead assigned to secondary metabolites. More can be read here.

Plant species will respond differently to climate change, and so will medicinal species. Some species will quickly adapt to new climatic conditions through natural selection within the ecosystem. Some species of medicinal plants may become extinct. Species that rely on each other (Co-existence) will be driven to extinction if they no longer co-occur in the same time or space.

Effect of elevated CO2 on productivity and quality of medicinal plants

In controlled environments, experiments have shown the beneficial effects of elevated CO2 on the productivity and quality of various medicinal products and constituents obtained from plants. This research was done under controlled conditions. Hence, further studies are needed to confirm the theory. Read the research article here, Archived.

Like animals, plants can migrate to higher latitudes or altitudes to avoid scorching temperatures. However, the fragmentation of tropical biomes resulting from rampant deforestation, agribusiness, mining, and infrastructure construction could significantly reduce the potential for successful plant migration. This leaves the adaptation capacity of plants narrow. More can be read here, Archived.

Status of endemic medicinal plants in Sri Lanka with climate change

Endemic plant species are considered more vulnerable to climate change and may face a high risk of extinction due to their confined geographic distribution. Most endemic plants are medically used by the people and not recorded formally. Some of them are, Depterocarpus zeylanicus, D.hispidus, Shore asp., Garcinia hermonii, Xylopia championii, Mesua nagassarium, Loxococcus rupicola, Atalantia rotundifolia, Caryota urens), Calamus sp., Kokoona zeylanica, Elattaria, and Coscinium fenestratum are highly threatened due to climate change which induces habitat destruction and degradation of micro-ecosystems.

Climate change, Invasive species, and medicinal plants

Over the past six decades, Sri Lanka has experienced a slow but steady increase in annual environmental temperature by 0.01–0.03°C. There is an increase in extreme events of rainfall and drought. Pests, diseases, and invasive species spread and thrive in new ranges, putting more pressure on fragile ecosystems, including medicinal plants. However, a linear correlation between climate change and Invasive Alien Species (IAS) cannot yet be identified. Sathischandra et al. (2014) reported that weeds and insect pests could be relatively higher due to extreme climate events. Read more here, Archived.

An article published by National Center for Biotechnology (NCBI) about traditional medicine in Sri Lanka says,

“The threat of extinction of certain species of plants and herbs is stressed, the causes being the destruction of jungles, the greater demand for raw materials for increased manufacture of traditional medicinal preparations, the absence of organized cultivation of medicinal plants, and unscientific harvesting. The compilation of encyclopedias of plants used in traditional medicine is highly recommended for every country interested in preserving the traditional systems of medicine.” 

In Conclusion

Even though further studies need to be carried out in order to understand the subject of the threat of medicinal plants to climate change, it’s evident that climate change is causing noticeable impacts on the life cycle as well as the distribution of medicinal plants in Sri Lanka.