A silent biodiversity loss threatens the Planet

An international study introduces the concept of dark biodiversity, which helps to understand the completeness of an ecosystem in relation to its natural potential. The greater the human pressure, the lower the ability of the system to proliferate

by Matteo Cavallito

 

Human activity impacts the Planet by generating a phenomenon that is as worrisome as it is difficult to capture: the loss of plant biodiversity. A widespread problem that affects even those natural areas seemingly not directly subject to anthropogenic pressure. This is supported by a group of researchers from different academic institutions who, in a study published in Nature, introduced a new concept defined as dark diversity. That is, the set of species that could live in a given place but are absent despite being present in the surroundings and, above all, compatible with the local environment.

Understanding the completeness of a system

“The problem is that over time, as we lose species due to human impact, we don’t see the number of species that are lost because we only see what we can perceive,” Viktoria Wagner, a University of Alberta professor and co-author of the research, explained in a statement, pointing out that this approach allows for a more complete picture of the problem by highlighting not so much the presence of species in a certain place as their absence.

“There’s a silent loss of biodiversity happening that might have gone unnoticed using the traditional tools,” Wagner explains. “The concept of dark diversity is a way for us to understand what species could have been there but are currently lacking.”

In short, dark diversity reveals how “complete” an ecosystem is in relation to its natural potential. Using this new approach, then, the researchers were able to develop a new metric called “community completeness” that measures the percentage of potentially present species that were actually detected at a given site. A completeness of 25 percent, to be clear, is proper of an ecosystem that hosts only a quarter of the species that, under normal circumstances, would be able to inhabit it.

Biodiversity is negatively correlated with surrounding human pressure

Carried out by DarkDivNet, a global network formed to explore the hidden biodiversity of plant communities, the study has involved 5,415 sites to date located in 119 regions in every continent, “To estimate community completeness, we compared the number of recorded species with the dark diversity,” the authors explain. Moreover, they add:

“In the sampled regions with a minimal human footprint index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly affected regions.”

Biodiversity, the authors explain in short, “is globally negatively related to the level of anthropogenic activity in the surrounding region.” Moreovtr, the study also points out that many potentially present species have now disappeared or, at any rate, can no longer establish themselves in still intact or semi-natural environments. “As well as causing species losses in directly affected locations,” the research states, in fact, “human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonization.”

Opportunities for restoration

On May 22, the world celebrates Biodiversity Day, an occasion to think about the phenomenon of its progressive loss, which, according to experts, poses no less serious threat than the climate crisis. The study, in this sense, makes an important contribution to efforts to combat the problem by introducing a new concept that enables the design of both targeted restoration interventions and conservation strategies on a larger scale.

The concept of dark biodiversity “Besides having the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation,” the research concludes. “Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.”