Photo by: veeterzy
In-situ and ex-situ conservation methods should not be considered equivalent strategies for protecting plant biodiversity. We must ensure for in-situ conservation (land preservation). This is especially true for biological hotspots. Ex-situ conservation (botanical gardens, gene and seed banks, or cryogenic preservation) can only supplement the rich genetic diversity that evolves in intact, wild ecosystems.
The ideal scenario for plants
Plants are much more complex than we usually imagine. Like humans, they develop in colonies, but unlike humans they are integrally involved with their surroundings. They depend on their relations to other species, they carry their history with them in their genetic code, and they respond evolutionarily to environmental threats. Plants have unique cycles of reproduction and sometimes their seeds remain obstinately dormant for years. What makes a seed burst into life still largely remains a mystery.
However, it is clear that fully developed plant communities such as old growth forests are the most respected emblem of natural beauty worth preserving. In such ecosystems, nature appears to work in perfect harmony. The plant species adapt perfectly to the climate and geological features and the ecosystem perpetuates itself by fertilizing the soil and cleansing the water while providing a breadth of possibilities for diverse species to coexist. Such a habitat produces vast genetic variation and reproductive stability for the species that call it home.
A strategic shift in conservation
When it comes to plant conservation, attempts to protect such ecosystems have proven nearly futile due to economic and developmental pressures. As a last resort, conservationists have adopted the hopeful practice of preserving seeds and genetic material in isolation from their natural habitats.
Defining In-situ and Ex-situ Plant Conservation
In simple terms, in-situ is “on-site” in Latin and ex-situ is “off-site.”
The main difference is that in-situ conservation practices keep a plant species in the context of its local, wild ecosystem, while ex-situ conservation practices remove a species from its local environment into either man-made environments such as botanical gardens or into storage facilities such as seed banks.
The terminology dilemma
The prefixes of these terms make them seem equal, though opposite, which is misleading. In-situ and ex-situ practices are most effective when ex-situ conservation supplements in-situ conservation. In-situ plant conservation should be given more of a priority due to its overall benefits for plant preservation.
An international discussion
The Convention on Biological Diversity (CBD) defines goals for both in-situ and ex-situ conservation for its signatories in Article 8 and Article 9, respectively. Article 9 begins its discussion of ex-situ conservation with the following disclaimer: “Each Contracting Party shall, as far as possible and as appropriate, and predominantly for the purpose of complementing in-situ measures.” Furthermore, it recommends planning for the reintroduction of species preserved by ex-situ means into their natural habitats.
To complement these measures, the Global Strategy for Plant Conservation outlines specific targets for 2011-2020 regarding plant diversity that involve both in-situ and ex-situ conservation methods for threatened plant species (those that are likely to become endangered in the near future):
- Target 7: At least 75 per cent of known threatened plant species conserved in situ.
- Target 8: At least 75 per cent of threatened plant species in ex situ collections, preferably in the country of origin, and at least 20 per cent available for recovery and restoration programmes.
Why are ex-situ and in-situ conservation methods frenemies?
In-situ conservation preserves more than simply the individual species it contains and it accounts for the fact that a species’ genetic makeup is not independent of its environment. It allows factors such as plant succession to occur. This is an ecological phenomenon in which plant communities colonize, establish themselves and then decompose in concert with other species undergoing similar cycles.
Plant succession enables natural evolutionary processes to occur and it is a theory that models plants within a community of different species. Within plant succession, each individual species is subject to natural selection, which promotes genetic diversity. Likewise mutually supportive symbiotic relations between species can form. None of these processes typically feature in ex-situ environments such as botanical gardens or seed banks.
While it is considered a cost-effective means of conserving plant diversity, ex-situ methods pose many difficulties. Ex-situ conservation efforts are only useful if seeds can be reintroduced into natural habitats in ways that preserve their genetic (allelic) complexity. Oftentimes, plant genomes change when they are grown in controlled or isolated environments due to the lack of succession and natural selection.
In addition, plant recovery and relocation from ex-situ storage is challenging because of the high number of recalcitrant seeds which are unable to grow due to the changes in environmental conditions. Factors such as plant vulnerability and the uncertainty about a plant’s fundamental suitability for different environments may also prevent successful reintroduction.
Reintroduction research is the key to ex-situ conservation and this research is far less developed than seed collection, which has expanded to include cryogenic methods. Without proper means for reintroduction, the result is a genetic bottle-neck in which only a fraction of genetic diversity can effectively be preserved through ex-situ methods.
Since it is clear that ex-situ conservation is not a reliable means to achieve conservation goals of genetic diversity for plants, continued education about the importance of in-situ conservation (land preservation) is vital to protecting the world’s rich biodiversity. While it is a more costly and difficult means, it must be impressed upon organizations, governments and corporations that it is the only fully viable means of plant diversity preservation.
A philosophical perspective on the importance of giving in-situ conservation precedence: https://dspace.library.colostate.edu/bitstream/handle/10217/39090/In-situ-Ex-situ-updated.pdf?sequence=1
A research paper on China’s response to GSPC which favors ex-situ conservation for economic reasons (without fully detailing the drawbacks): https://www.researchgate.net/profile/De-Zhu_Li/publication/26884437_The_science_and_economics_of_ex_situ_plant_conservation/links/55b0461608aeb92399171f73.pdf
On the difficulty of reintroducing rare species populations in China: https://www.srs.fs.fed.us/pubs/ja/2012/ja_2012_ren_003.pdf
On the effective measurement of plant species vulnerability to include both current threats and climate change threat analysis: http://plantconservation.weebly.com/uploads/9/5/6/4/95648510/smith_et_al_2016_shifting_targets_-_spatial_priorities_for_ex_situ_plant_conservation_depend_on_interactions_between_current_threats_climate_change_and_uncertainty.pdf