When a disturbance occurs in a natural area, generally the same ecosystem is responsible for restoring the environment, with the contribution of nearby seeds. In fact, intermediate disturbances enhance biodiversity by creating heterogeneous areas in the ecosystem.
Each ecosystem has its level of resilience or capacity to absorb disturbances of a certain magnitude while maintaining its structure, its dynamics and its functions intact, and thus preserving the ability to return to the situation prior to the disturbance. Ecosystems that are more complex, richer, more biodiverse and with a greater number of interactions between their parts tend to have greater resilience.
However, sometimes, due to human activities, disturbances of great magnitude occur that exceed the resilience of the ecosystem, leaving great devastation in their wake. The recovery of this ecosystem becomes a complicated task, which implies a large amount of time and energy, in a process of secondary succession that is not always successful.
Restoring the ecosystem
Fortunately, science provides us with tools that help the recovery process more quickly and efficiently. Among all the tools, repopulation stands out.
It is important, when undertaking repopulation tasks, that the plants to be planted in the area belong to species in one of the ecological succession phases of the ecosystem.
However, it is often not enough to have the species. Some species have very wide distribution areas in the world, and form, in different geographical regions, populations that are genetically very different from each other. When repopulating an area, therefore, it is not only relevant to do it with species native to that region, but it must also be done with individuals that belong to the same genetic population , and not to others.
The importance of genetic population
In ecological restoration in general, and in plant repopulation in particular, the goal is always to create new populations that preserve the original regional gene pool while maintaining a genetic diversity large enough to allow adaptation of the restored ecosystem to possible environmental changes.
The genetic population can vary from one region to another, despite belonging to the same species, due to differences in the selective pressure to which the different populations have been subjected. Each population is adapted to the specific conditions of its environment, sometimes very different from the environment of other conspecific populations.
Restoring an environment using a different genetic population than the one that existed in the area can have unintended consequences, in several ways.
On the one hand, it may happen that the population used for the repopulation is not well adapted to the environment to be repopulated, and consequently, the repopulation will not be successful. This would imply not only a loss of resources —economic, ecological and time— in an action doomed to failure, but also the delay that this entails means that a better designed future restoration using the original genetic populations would not be efficient either; because the time elapsed since the disturbance is easy to cause a loss of soil that makes the task of repopulating even more difficult, or impossible.
On the other hand, and in the opposite direction, if the reintroduction is successful, the new genetic population of an exotic character can be overly successful, become invasive and contaminate the gene pool of neighboring populations through hybridization.
Thus, for a correct ecosystem restoration, it is essential to use individuals belonging to the same genetic population . But, in a devastated environment, there may not be enough plants left to produce the number of seeds needed, or the population having been decimated, the resulting genetic diversity may not be sufficient. And it is at this point where germplasm banks come into play.
The germplasm bank, the optimal collection of seeds
A germplasm bank or seed bank is a facility where a large number of seeds of multiple plant species are preserved, in viable conditions, according to their genetic populations.
When an ecosystem restoration is necessary, these banks become very useful, almost essential. They work in a similar way to a blood bank , where the fluid is preserved and classified according to blood type and RH, so that the patient receives the most appropriate product.
From germplasm banks, previously collected seeds can be obtained, which belong to the same devastated genetic population, and which preserve sufficient genetic variability for ecological restoration to be optimal.
In fact, seeds of regional origin conserved in germplasm banks can produce restored populations of the same genetic population, and at the same time, be genetically diverse at levels similar to those found in wild populations.
Unfortunately, not all seeds can be kept in a genebank. At the moment, the only way to preserve populations of certain species is in vivo, for example, in botanical gardens. However, cryopreservation technology has come a long way in recent years, which will increase the chances of preserving more different types of seeds.
References:
Höfner, J. et al. 2022. Populations restored using regional seed are genetically diverse and similar to natural populations in the region. Journal of AppliedEcology, 59(9), 2234-2244. DOI: 10.1111/1365-2664.14067
McKay, J. K. et al. 2005. «How Local Is Local?»-A Review of Practical and Conceptual Issues in the Genetics of Restoration. Restoration Ecology, 13(3), 432-440. DOI: 10.1111/j.1526-100X.2005.00058.x
Vanavermaete, D. et al. 2020. Preservation of Genetic Variation in a Breeding Population for Long-Term Genetic Gain. G3 Genes|Genomes|Genetics, 10(8), 2753-2762. DOI: 10.1534/g3.120.401354
Walters, C. et al. 2021. The unique role of seed banking and cryobiotechnologies in plant conservation. PLANTS, PEOPLE, PLANET, 3(1), 83-91. DOI: 10.1002/ppp3.10121
