This series of posts deals with threats to biodiversity from a botanical perspective. There is no lack of evidence for climate change and it’s easy to become overwhelmed and pessimistic. But the only way forward is to learn more about what is happening and why, and then to take action based on that knowledge. One example of the botanical community’s efforts is a report published by the Royal Botanic Gardens, Kew, with contributions from a global roster of researchers. State of the World’s Plants and Fungi 2020 is a useful blend of optimism and caution, presenting how biodiversity is catalogued, what is being learned about it, and how it can be preserved and also used into the future. This latest report is supplemented with articles in a special issue of Plants, People, Planet as well as with a virtual symposium. Earlier, Kew had published separate reports on plants and on fungi, but it made sense to combine them since this is how they are found in the world.
It’s no surprise that Kew would have a leadership role in biodiversity research with its impressive staff and the world’s largest herbarium. It also has a long history of studying plant diversity in developing nations, though granted, for a good portion of this history Kew’s efforts were on behalf of the world’s largest colonial power. Garden administrators directed far-flung collectors, who relied on the expertise and labor of countless indigenous assistants and enslaved persons in finding plants that often proved economically important to the British (Brockway, 1979). The past and future are intertwined at Kew in complex ways in its living and preserved plant collections. Kew sponsored a symposium on the recent work of digitizing its collection of Miscellaneous Reports that colonial botanic gardens sent to Kew. It is an important step in decolonizing its collection and was a fascinating look into how plants and plant products moved throughout the British Empire.
The present Kew report notes that 1942 new vascular plant species were described in 2019. Many new finds were recently collected, but herbaria harbor plants awaiting identification and in some cases discovery as new species. There is no solid estimate of the earth’s total plant diversity, of how many different plants exist. The best record of known plants runs to around 350,000, with 325,000 of them flowering plants. The situation with fungi is cloudier. Almost 150,000 fungal species have been named and described; 1,886 were added in 2019. With much research now being done on fungi, greater diversity is becoming apparent, and estimates of the number of fungal species now range from over two to nearly four million. To me this is one of the most fascinating aspects of the report: how the power of the fungal world is finally coming to be appreciated. Two books that have done much for fungal publicity are Peter Wohlleben’s The Hidden Life of Trees (2016) on how fungi support plant life and Merlin Sheldrake’s Entangled Life (2020) on how fungi influence so much of the living world.
The Kew report notes that the great biodiversity in tropical areas means some countries, though explored for centuries, are still yielding many discoveries. Brazil, Madagascar, India, and South Africa have been collection areas from the sixteenth century on. There have been a number of projects where these sites have been revisited, with older collections used in planning surveys. The new work may recollect the same specimens, which can be used in genetic comparisons with the older plants. Not finding some species points to changes in the habitat due to climate change or other factors, and not surprisingly there may be new species found as well.
Island ecosystems are particularly rich in endemic species found nowhere else: 83% of Madagascar’s 11,138 native plant species are limited to this island, making learning about and protecting its flora especially important. A recent study in New Guinea reports that it has the world’s richest island flora with 13,634 species, 68% endemic (Cámara-Leret et al., 2020). This is the first comprehensive plant list for the island, and the study could be a model for future work in other areas, though it may still be quite incomplete. There are 3,962 tree species on the list, which seems impressive, but the number found in an inventory of the Amazon region was over 10,000. In South America, researchers surveyed all the plants in almost 2000 study plots, a time-consuming and labor-intensive cataloguing job particularly under difficult conditions. In New Guinea, only 300 plots were surveyed, which may explain the lower tree species count. This suggests that discovering biodiversity is both hard work and not near its end, while these species-rich areas are under increasing threat from development (Novotny & Molem, 2020).
There are many factors involved in estimating biodiversity. It is not just the density of sampling, but where the sampling is done. Studies of the geographic locations on herbarium specimens has uncovered many collection biases because botanists, being human, tend to collect relatively close to home and even during exploration, find some areas easier to access than others. For former colonies, the regions around botanic gardens were often well studied, or were along supply routes, or near seaports or other urban areas. Species-rich regions of South Africa were explored from the 17th century (see image above), but there were no collections in some areas until the end of the 19th century when they were opened to agriculture (Cowell, 2020). Few collections were made in highly diverse portions of Cameroon until they were surveyed over a decade beginning in 2004; 2240 plant species were found with about a tenth under threat of extinction (Demissew, 2015).
Brockway, L. B. (1979). Science and Colonial Expansion: The Role of the British Royal Botanic Gardens. Interdisciplinary Anthropology, 6(3), 449–465.
Cámara-Leret, R., Frodin, D. G., Adema, F., Anderson, C., Appelhans, M. S., Argent, G., Arias Guerrero, S., Ashton, P., Baker, W. J., Barfod, A. S., Barrington, D., Borosova, R., Bramley, G. L. C., Briggs, M., Buerki, S., Cahen, D., Callmander, M. W., Cheek, M., Chen, C.-W., … van Welzen, P. C. (2020). New Guinea has the world’s richest island flora. Nature, 584(7822), 579–583. https://doi.org/10.1038/s41586-020-2549-5
Cowell, C. R., Anderson, P. M. L., & Annecke, W. A. (2020). Historic herbarium specimens as biocultural assets: An examination of herbarium specimens and their in situ plant communities of the Agulhas National Park, South Africa. People and Nature, 2(2), 483–494. https://doi.org/10.1002/pan3.10087
Demissew, S., Beentje, H., Cheek, M., & Friis, I. (2015). Sub-Saharan botanical collections: Taxonomic research and impediments. In I. Friis & H. Balslev (Eds.), Tropical Plant Collections: Legacies from the Past? Essential Tools for the Future? (pp. 97–114). Stockholm: Scientia Danica.
Novotny, V., & Molem, K. (2020). An inventory of plants for the land of the unexpected. Nature, 584(7822), 531–533. https://doi.org/10.1038/d41586-020-02225-4
Sheldrake, M. (2020). Entangled Life. London: Bodley Head.
Wohlleben, P. (2016). The Hidden Life of Trees. London: Harper Collins.