A regenerated forest can appear tall, dense, and verdant. Revitalized wetlands can hum with insects and flutter with birds. However, upon closer inspection, scientists have discovered 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, aiding in their population rebound. Yet, recent studies indicate that not all species return at the same pace. Some of the smallest, least conspicuous inhabitants may remain scarce or missing for decades, potentially impacting other species.
Ellen Macdonald, a botanist from the University of Alberta, has dedicated her career to studying forests, focusing not on the trees but on the minute flowers, mosses, liverworts, and lichens that thrive in their shadow, among their roots, or on their bark’s textured surfaces.
Macdonald emphasized the vast diversity of species in forest ecosystems compared to tree species. To an average observer, a regenerated forest decades after logging may resemble an untouched one, brimming with tall trees, birds, and insects. However, Macdonald noted a subtle sense of something amiss while walking through regrown coniferous boreal forests.
Through a combination of her research and global data, Macdonald investigated the timeline for plant and animal recovery in boreal forests post-clearcutting. The research, recently published in the journal Nature Sustainability, revealed that birch and aspen forests and their inhabitants typically recover within 25 years, whereas conifer forests require significantly longer. In conifer forests, understory plants, particularly lichens, mosses, and liverworts, took 85 years or more to reappear, with some species still absent even after a century.
This pattern of delayed recovery is not unique to boreal forests. Scientists studying restored wetlands and other habitats have observed a similar phenomenon where seemingly healthy environments lack certain less visible species.
Viktoria Wagner, an associate professor at the University of Alberta, described this decline as a “silent form of loss,” leading to a reduction in species diversity at individual sites. Such “dark diversity” has been documented among plants globally, including algae, which play crucial roles in ecosystems.
The absence of certain species can hinder recovery processes and have far-reaching ecological consequences. Algae, despite their small size, significantly influence oxygen availability and global photosynthesis, impacting various species within the ecosystem.
Understanding these recovery patterns could guide landscape managers in preserving more species. Macdonald suggested that selective harvesting or partial extraction in conifer forests may be more beneficial than clearcutting, considering the long recovery times for understory plants.
The preservation of biodiversity necessitates more than safeguarding isolated habitats; it requires maintaining and restoring sufficient habitat to support species across landscapes. Active interventions are essential to combat ongoing species losses and ensure the persistence of vital ecosystems.