A rejuvenated forest can appear tall, vibrant, and verdant. Revived wetlands can hum with insects and flutter with birds. However, upon closer inspection, scientists are discovering that some of the tiniest inhabitants, such as specific mosses, lichens, algae, and fungi, are often still absent.
The restoration of habitats like forests and wetlands can aid in saving declining species of animals and plants, assisting in their population recovery. Yet, recent studies reveal that not all species return at the same pace. Some of the most inconspicuous inhabitants may remain scarce or missing for decades, potentially impacting other species.
Ellen Macdonald, a botanist at the University of Alberta, has dedicated her career to studying forests, focusing on the minute flowers, mosses, liverworts, and lichens that thrive in their shade, among their roots, or on the textured surfaces of their bark.
According to Macdonald, a regenerated forest several decades post-logging may outwardly resemble an untouched one, brimming with tall trees, birds, and insects. However, she noted a sense of something amiss while traversing regrown coniferous boreal forests, even if the exact nature of the absence wasn’t immediately discernible.
To delve deeper into this phenomenon, Macdonald amalgamated her research with global data to investigate the timeline for plant and animal reemergence as boreal forests regenerate following clear-cutting.
Published recently in the journal Nature Sustainability, the study revealed that birch and aspen forests and their inhabitants seemed to recover within 25 years, while conifer forests took significantly longer. In conifer forests, understory plants — particularly lichens, mosses, and liverworts — required 85 years or more to reappear, with some species still absent even after a century of available data.
The pattern observed in boreal forests extends to other ecosystems, as scientists studying restored habitats like wetlands have also noted the continued absence of less visible species despite the overall appearance of health.
German botanist Michael Melkonian, in a past interview with CBC News, described his observations of restored wetlands near his home in southern Germany, highlighting the stark contrast between the superficially flourishing environment and the limited presence of certain species, like desmid algae.
Viktoria Wagner, an associate professor at the University of Alberta, characterizes this decline as a form of “dark diversity,” where species gradually vanish from once-populated areas, reducing overall biodiversity within individual sites.
The disappearance of certain species can have subtle yet far-reaching consequences. Algae, despite their small size, play a significant role in global oxygen availability and food production through photosynthesis. As diversity diminishes, these effects cascade through ecosystems, impacting various organisms.
Understanding these ecological dynamics can guide landscape managers in preserving a broader array of species. Macdonald suggests that selective or partial harvesting of conifer forests instead of clear-cutting could better support the recovery of mosses, lichens, and other understory plants that rely on shade and mature trees for habitat.
In addition to terrestrial habitats, the preservation of algal diversity faces threats worldwide. Melkonian and his colleagues have undertaken the collection and cultivation of over 5,000 algal strains to safeguard these vital species. Wagner emphasizes the need for active interventions to combat ongoing species loss and stresses the importance of maintaining sufficient habitat for species to flourish across landscapes.
Ultimately, the silent disappearance of species underscores the necessity of comprehensive biodiversity conservation efforts beyond isolated habitat protection. Active measures are crucial to sustain species diversity and promote ecosystem resilience in the face of ongoing environmental challenges.