Photo credit: www.sciencedaily.com
The global impact of human activity on biodiversity is proven to be profoundly harmful, with both the number and composition of species in decline. This alarming conclusion stems from a comprehensive study conducted by researchers from the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and the University of Zurich, published in the scientific journal Nature. Representing one of the most extensive investigations into this issue, the study sheds light on the critical state of ecological diversity across the planet.
The threat to biological diversity is becoming increasingly evident, as ecosystems worldwide face significant pressures resulting from human actions. Historically, individual studies have explored various aspects of this phenomenon, either focusing on specific geographic locations or examining particular environmental impacts, making it difficult to ascertain overarching trends. Thus far, no comprehensive synthesis has fully addressed how pervasive human interventions have altered ecosystems globally.
To tackle these research limitations, the Eawag and University of Zurich team carried out an unprecedented synthesis study. They reviewed approximately 2,100 existing studies that evaluated biodiversity at nearly 50,000 sites impacted by human activity, compared against an equal number of reference sites unaffected by such influences. The research spans diverse environments, including terrestrial, freshwater, and marine habitats, encompassing a wide range of organisms from microbes and fungi to flora, invertebrates, and higher vertebrates. As Florian Altermatt, a professor at the University of Zurich and lead researcher at Eawag, noted, this study stands out as one of the largest examinations into human impacts on biodiversity conducted globally.
Species numbers are clearly declining
The study’s results are clear and unequivocal, demonstrating substantial human-induced damage to global biodiversity. François Keck, the lead author and postdoctoral researcher in Altermatt’s team, explained that they investigated the effects of five prominent human pressures on biodiversity: habitat alteration, direct exploitation of species through activities like hunting and fishing, climate change, pollution, and the introduction of invasive species. The findings reveal a significant impact from all five factors across various ecosystems, affecting all groups of organisms.
On average, species richness at impacted sites was nearly 20% lower than at those that were unaffected. Notably, vertebrate populations, including reptiles, amphibians, and mammals, exhibited particularly severe declines, often with smaller population sizes, which increases their risk of extinction.
Species communities are shifting
The study also highlights that biodiversity loss extends beyond mere species extinction. According to Keck, the pressure of human activity is reshaping the very composition of species communities. For instance, in high-altitude regions, specialized plant species are at risk of being replaced by lower-altitude species due to climate warming. Consequently, even if species numbers at specific locations remain unchanged, the overall biodiversity and functionality of ecosystems could suffer harmful impacts, particularly if key species with specific ecological roles, such as certain plants that stabilize soil, disappear. The most pronounced shifts in species community composition were observed among microbes and fungi, possibly due to their rapid life cycles and broad dispersal capabilities.
The researchers found that environmental pollution and habitat alteration notably contributed to declines in both species numbers and community structures. Altermatt pointed out that drastic changes, such as deforestation or significant land conversion, represent clear threats to biodiversity. Furthermore, pollution from both accidental events, like oil spills, and deliberate practices, such as pesticide use, adversely affect the organisms inhabiting these environments. While climate change also poses substantial risks to biodiversity, Altermatt emphasized that its full impact might not yet be entirely evident.
The findings are cause for alarm
The third pivotal aspect the research examined was the homogeneity of species communities across different sites. Large-scale agricultural practices were found to promote more uniform landscapes, leading to increased similarity in species communities within those areas. Results varied—some studies indicated heightened homogenization, while others noted emerging diversity, particularly at local levels. However, the researchers caution that any observed variability may not be a positive sign. Fluctuations could reflect temporary changes in severely impacted habitats rather than genuine recovery. Altermatt warned that signs of potential community collapse are notable when human influences are particularly severe.
The implications of this study are significant; it underscores the necessity of evaluating biodiversity not only through species count but also by considering community composition changes. The findings are alarming due to their clarity and global applicability and will serve as a reference point for ongoing biodiversity research and conservation strategies. Keck remarked that the research provides critical insights into which human activities are most detrimental to biodiversity, highlighting the urgent need for targeted goals to address these trends effectively.
Source
www.sciencedaily.com