Why conserve a species? This simple question seems to have a complex multitude of answers. First, one could argue that each species has an intrinsic value – on account of its beauty and uniqueness, that makes it worthy of conservation. Secondly, one would want to conserve a species if it is of use to humankind – whether it is economically valuable, traditionally utilised, culturally significant or has medicinal properties. This reason also encompasses those species whose usefulness is yet unknown, and may be revealed by further research. Thirdly, one may assert that each species is a result of a completely stochastic process of evolution that has spanned millions of years and this makes each species akin to an ancient relic, one whose occurrence represents a very slim margin of probability. Further, this means that each species represents a large genetic reserve, making a wild population of that species a store of genetic variability within that taxon. And finally, one can choose to conserve a species because it belongs to an ecosystem – tied into a complex web of ecological relationships, mutualisms and interspecific interactions – which implies that its loss would affect each link in this intertwined web and have repercussions that are far too complex to anticipate.
In the past two decades, the habitats of many species have seen decline due to human intervention, forcing many species into positions of vulnerability with regards to extinction. In the case of plants, this has led to various ex-situ conservation efforts, the majority of which focus on propagating the endangered plant species and reintroducing it into the wild. These efforts are typically headed by botanical gardens and similar scientific institutions, and often results in a situation where a species may only exist in botanical collections, and become completely extinct in the wild. Take the example of café marron or Ramosmania rodriguesi for example, which was considered extinct till 1979, at which point a single tree was discovered and cuttings sent to Kew Gardens – with the cultivated population effectively outnumbering the natural population several times over. In other scenarios, a species in already popular in cultivation later becomes extinct in the wild due to over-collecting, habitat loss or environmental degradation. The examples are plentiful – the most popular being the Hibiscus (Hibiscus rosa-sinensis), but also including wide-ranging families and genera including Aloe descoingsii, Frerea indica and others. For plants such as these which exist almost exclusively in cultivation, the imperative question becomes whether cultivation equals conservation.
Returning to our question of why conserve a species, while cultivation seems to completely satisfy the first two reasons, its efficacy in fulfilling the latter two is met with certain complications. The first issue is genetic. The processes of breeding, pollinating and propagating a species in cultivation significantly alters its genetics. Vegetative propagation (commonly used in the nursery trade but avoided in scientific conservation efforts) does not create any genetic variation; hybridisation and cross breeding introduce genes into the genome of an organism which may not have occurred in nature; and self-fertilisation to establish true-breeding lines (a common practice when growing plants for commercial trade) limits genetic diversity and may lead to issues with inbreeding. The combined effects of these processes of cultivation do preserve the species, but do not conserve its genetic natural genetic characteristics. Of course, having some genes is better than having no genes, and preserving a species in cultivation is still extremely valuable.
The second issue is ecological. A species maintained exclusively in cultivation does not participate in the ecological framework in which it would have existed in nature, and is excluded from overarching evolutionary processes which operate in an ecosystem. Take a species which has developed a plant-pollinator specificity and evolved a mechanism to evade predation. In cultivation, both these ecological factors (the pollinator and the predator) are removed, and this will change the evolutionary and genetic trajectory of the species. Further, from an ecological standpoint greater diversity typically translates into greater resilience for an ecosystem, so even if a species is extant in cultivation, its native ecosystem is weaker for its loss. On the flip side, there are ecological positives to cultivation as well. Even cultivated plants such as those in public parks, gardens and agroforests become parts of novel ecologies, and serve vital roles in these new ecosystems. And theories such as ‘Ecological fitting’ propose that certain species introduced into ecosystems from cultivation could occupy the ecological niches left empty by now-extinct species.
Even apart from the points mentioned above, cultivated plants have conservation value. Most importantly, they help educate and sensitise people (especially members of the general public) about the pressing issue of the loss of biodiversity and the need for its protection. They do undeniably provide a vital baseline population for species that are endangered in the wild, and can be used to regenerate wild populations; as was the case with the earlier mentioned Ramosmania rodriguesi, which was reintroduced to its native habitat on the island of Rodrigues in the Indian ocean. But I still question whether plants reintroduced from cultivation will have enough genetic diversity to form successful and stable wild populations. It feels strange for me to be asking these questions, considering I hope to work in ex-situ conservation someday, but I do not intend to sound pessimistic, rather to stimulate growth.
A discussion as complex and multifaceted as this one is impossible to see only from one point of view, and requires different perspectives. And any discussion is made richer by differing voices and opinions – so I invite you to add yours below!