The researchers Cristina González Montelongo and Israel Pérez Vargas from the Department of Botany, Ecology and Plant Physiology at the University of La Laguna have recently published a study in the journal ‘Journal of Fungi’ investigating the epiphytic lichens—life forms that thrive on tree bark—to assess the state of conservation of Monteverde or Canarian laurisilva.
This investigation has revealed signs of an “extinction debt” in Tenerife, likely stemming from the decline of this habitat in recent centuries.
Moreover, it has highlighted La Gomera as exhibiting a greater degree of laurel forest conservation in comparison to Tenerife and La Palma.
Following a significant disturbance in an ecosystem, such as deforestation or fire, species closely associated with it can persist in unaffected refuges for some time. Consequently, they do not vanish immediately when the disturbance takes place, as reported by ULL in a statement.
The species continue to exist, the researchers explain, yet they no longer possess the essential conditions for survival, making their extinction a mere matter of time unless actions are taken to mitigate the damage.
Lichens are dual organisms formed by at least one fungus and a photosynthetic partner that exist in a close, obligatory relationship. These organisms, found in all known terrestrial ecosystems and capable of thriving on almost any substrate, have been extensively employed due to their unique attributes as bioindicators and biomonitors of environmental pollution, air quality in urban and industrial areas, and land-use changes, among other variables.
This research utilised lichens to ascertain the conservation status of the Canarian monteverde, a endemic forest of the Macaronesian region that is significantly at risk.
However, until now, the impact of human activities on this forest environment through the study of lichens had not been examined.
The research team established 18 study plots, each covering 100 square metres on the islands that feature the most extensive representations of Monteverde in the archipelago: La Palma, La Gomera, and Tenerife.
Thus, the epiphytic lichens of the prevalent species in this forest (holly, laurel, faya, and heather) were examined, and lichen samples were collected from a total surface area of 500 square centimetres at each cardinal orientation (North and South) for subsequent laboratory identification.
A total of 165 lichen species were identified: 96 species in Tenerife, 82 in La Palma, and 70 in La Gomera.
Only 24% of species shared
Out of all species, only 24% were shared across all the islands: 9% between La Palma and Tenerife, 6% between La Gomera and Tenerife, and 5% between La Palma and La Gomera.
The variation in species counts across the islands did not reveal significant differences, which contradicts the prevailing theory of island biogeography, which suggests that larger islands host a greater number of species than their smaller counterparts, as noted by ULL.
To examine whether a distribution pattern of lichens has emerged due to the human transformation of the Canarian monteverde, the research group analysed the distribution of these organisms in relation to both the actual vegetation (currently present in an area) and the potential vegetation (to which natural succession would progress if human intervention ceased).
It was during this analysis that indications of a potential extinction debt in the epiphytic lichen diversity of the Canarian Monteverde were uncovered.
To verify if this phenomenon is occurring in the Canarian monteverde regarding lichens and, consequently, to evaluate the conservation status of the monteverde, the team assessed the areas of potential and actual vegetation as if they were islands and observed that the most significant disparities between potential and actual Monteverde were in Tenerife, followed by La Palma, and lastly La Gomera.
This data indicates that La Gomera offers the most representative examples of Canarian Monteverde, currently protected under the Garajonay National Park.
Conversely, on Tenerife, the overall area currently occupied by the monteverde should not yield such a high diversity of species if the theory of island biogeography is acknowledged.
