Conserving threatened trees

Nearly 30% of the world's approximately 59,000 tree species are now threatened with extinction and 142 tree species have already gone extinct. Of the 2600 tree species in India, at least 469 species are listed in various threat categories as per the IUCN Red List of Threatened Species. Among the world's ecosystems, tropical rainforests are particularly renowned for their rich diversity of trees and this is true within countries like India as well, where regions such as the Western Ghats are home to around 900 tree species.

A significant number of these trees are also endemic, found nowhere else in the world, particularly in the southern reaches of the Western Ghats such as the Anamalai Hills. Beginning in 2020, we began studies and conservation efforts focused on the following 11 threatened tree species of the Anamalai rainforests.

We carried out intensive field surveys in 29 sites along 65 trails of 113.35 km total length in rainforest fragments of the Valparai Plateau and in mature tropical rainforests within the Anamalai Tiger Reserve. We recorded 1948 individuals of the 11 target species and laid 620 plots to record measurements and associated species. We also published our past vegetation data with over 12,500 occurrences of 270 tree species on the Global Biodiversity Information Facility (GBIF).

Our survey resulted in significant new distributional records of CR species including a new population record of D. bourdillonii in Tamil Nadu with at least 40 mature trees, which is significant given that the earlier-known global population was less than 250 trees. We found multiple sub-populations of Phyllanthus anamalayanus in the Valparai Plateau and ATR. The rare Palaquium ravii (EN), earlier known from very few records in the southern Western Ghats, was found in 3 small clusters. Species such as P. anamalayanus and Orophea thomsonii were found to be locally abundant.

The information generated on geographic and elevational ranges, besides abundance information, along with compilation of past records that yielded around 2000 occurrences, was used for species distribution models and IUCN Redlist threat assessments. While the new findings on species occurrence and significant local populations was promising, models of distribution under future climate in 2061 – 2080 predicted range reductions in six species (including near-extinction for two species). Some increases in range for three species, and no substantial change for two species were also predicted. This analysis indicated the importance of identifying and conserving climatic refugia that can enable the persistence of tree species under anticipated climate change.

To bolster the populations of these threatened trees, we also raised them in our rainforest plant nursery and planted them in our restoration sites. Between 2020 and 2023, we planted over 6200 seeds of the 11 target species, raised a stock of 2500 seedlings and saplings in the nursery, and planted 1227 saplings of the 10 species in our restoration sites. These efforts are being continued in successive years for a wider range of threatened tree species. To generate conservation awareness of these threatened trees, we published an informative illustrated booklet, Last Ones Standing, available in English and Tamil.