Plant Conservation: Not One [species] Less

Fascination of Plants: Preserving a Green Planet

Since 2012, the 18^th of May was chosen for the celebration of the “Fascination of Plants” day, a global initiative to showcase the magic of the plant kingdom and to stress the importance of plant research. No doubt, plants are essential for life on earth: without them, humans would be deprived of food and non-food products. Plants also provide fundamental “ecosystem services”, including CO₂ capture and O₂ release, that make animal existence possible.   

Instead of reflecting on what life on earth would be like without plants, let’s be positive and think about what the planet would be like if not a single plant species got lost. Above all, protecting plant biodiversity will be crucial to increase the resilience of natural and artificial ecosystems in a changing environment. Therefore, plant conservation initiatives should pursue the ambitious target of “zero plant extinction” as suggested by Richard T. Corlett – Emeritus Professor at the Center for Integrative Conservation, Xishuangbanna Tropical Botanical Gardens, Yunnan (China) – in a review recently published in the journal Trends in Plant Science.

Prof. Corlett first introduces the main factors that threaten plant life – such as changes in land use that are leading to habitat degradation or even destruction, biotic stresses that affect plant health, and abiotic stresses that impact plant growth. Then, he calls for urgent actions to prevent the extinction of diverse plant species by preserving and restoring ecological communities. Good news: plant conservation is relatively cheap and can take advantage of already existing protected areas. Bad news: conservation projects are facing several societal and scientific challenges.

Zoocentrism in Conservation Strategies

The International Union for Conservation of Nature’s (IUCN) established the Red List of Threatened Species in 1964, which became the gold standard for conservation assessment worldwide. The Red Data Book divides species under study into 9 categories (i.e., Not Evaluated, Data Deficient, Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild, Extinct) and provides a wide range of information – from taxonomic data to the geographic range and threads for species survival over time. Strikingly, almost 100% of described vertebrates have been assessed, while only 15% of identified plants have been covered – with an alarming 70% of cycads at risk of extinction! Moreover, most conservation initiatives have established protected areas to safeguard flagship species of animals but very little attention has been paid to plant species. This underrepresentation is likely associated with plant blindness that affects not only the general public but also policymakers and the scientific community.

Plant Conservation: What and How

WHAT: the first steps are the selection of the plant species to be protected and the determination of its ecological range. Besides endangered species, locally adapted species should also be preserved as large genetic diversity can increase the adaptive potential of populations to fluctuating environments.

HOW: there are two major types of conservation, in situ and ex situ.

In situ conservation refers to the perpetuation of threatened plant species in protected areas or the preservation of biodiversity hotspots in the wild. Though, this strategy requires regular monitoring and management of species at risk (see also Important Plant Areas program).

Ex situ conservation refers to the generation and maintenance of backup for plant species. A good option is the long-term storage of dry seeds in SEEDBANKS, such as the Svalbard Global Seed Vault which preserves frozen seeds of almost 20% of all spermatophytes at -180ºC. Although this option is cheap and requires small-size spaces, it cannot be used for all species since some recalcitrant seeds have reduced longevity or high sensitivity to desiccation or low germination rate. In the case of “exceptional plants”, an alternative is the storage of somatic tissues in CRYOBANKS for future propagation. Yet, this alternative is expensive and procedures for cryogenic storage difficult to optimize.

Another interesting opportunity is to cultivate selected plant species in public and private places. A clear example is the network of botanical gardens that have been preserving one-third of specimens identified from the first botanical explorations to the present day. These green infrastructures require big spaces to grow living collections and funding to cover management costs but also provide materials for outreach and research activities.

The last futuristic approach relies on de-extinction – the use of sequencing data from extinct species to manipulate the genome of an extant relative and recreate archaic plants. Will increasing efficiency of protocols to extract ancient DNA and decreasing costs of Next Generation Sequencing facilitate the creation of “Green Jurassic parks”?

In his review, Prof. Corlett supports an integrated conservation strategy that encompasses both in situ and ex situ approaches, but he states that “preventing extinction in the wild is always preferable to reversing it, since it preserves interactions lost in captivity”.

Plant Conservation: Challenges and Opportunities

To achieve the zero-plant extinction target, conservation programs claim “more money, more space, more people and more local interventions”. Long-term funding is needed to establish new protected areas and facilities as well as to set up procedures and techniques that can be applied to all land plants. Expertise is also required for the correct identification and accurate description of new species, especially in tropical regions that are rich in biodiversity.

Nevertheless, old (but gold) and new tools can be instrumental to fight against biodiversity loss. Indeed, thousands of HERBARIA (i.e., inventories of dried plant specimens) worldwide provide information that can be used in the assessment of plants under threat. Digitization (e.g., scanned images, transformation of handwritten to transcribed labels) and automated validation by machine learning can be employed to improve plant identification and selection, although human knowledge is still required for final quality checks. Also, open access to digital resources can increase the participation of amateur naturalists in citizen science projects, thus accelerating these processes.

READ THE ARTICLE
Corlett, R.T. (2023) “Achieving zero extinction for land plants,” Trends in Plant Science. Available at: https://doi.org/10.1016/j.tplants.2023.03.019.