Biological invasions and global change: impacts of biotic homogenization and challenges for biodiversity conservation
The phenomenon of global change is defined as a set of environmental alterations driven by human activities, related to the modification of ecological processes that determine the ecosystem functioning. Within the components of global change, there are complex processes such as global warming and climate change, interacting with variations in land use, desertification processes, and alterations in the ecological balances of biodiversity in terms of its composition, distribution, structure and functioning.
In this context, biological invasions are one of the main causes of the current global biodiversity crisis. They are recognized as complex ecological processes derived from human activity, one of the main threats to biodiversity conservation, and one of the key drivers of global change.
Human activities such as increased global connectivity through trade routes and the exchange of goods and services have facilitated species crossing biogeographic barriers that delimit their natural distribution ranges (such as oceans, mountains, and deserts), leading to species exchanges between different regions of the planet. Thus, species can establish themselves in new environments and, under certain conditions, reproduce and expand, invading ecosystems and displacing native species, with impacts at multiple scales and at different levels of biodiversity organization.
Because they involve species exchanges worldwide, this phenomenon has been recognized as one of the most conspicuous manifestations of global change, with species introductions resulting in the reconfiguration of the geographic distribution of biodiversity, contributing to the process of global homogenization. Biotic homogenization is defined as the increase in compositional similarity between originally dissimilar regions. Different studies suggest that the complexity of biological invasions is due to the spatial and temporal dynamics of the geographic range of species, whose magnitude depends on ecological and evolutionary processes operating at different scales and hierarchies, as well as multiple factors and processes derived from different scientific disciplines. An example of this is the interactions between tree and shrub invasions and forest fires in central-southern Chile, where invasion processes related to rapid climate changes and land use changes converge with variations in the intensity and extent of disturbances, causing multiple impacts on human activities and the flows of matter and energy in ecosystems.
Regarding the impacts generated by invasive species on recipient ecosystems, changes have been observed in ecosystem processes such as primary productivity, nutrient cycles, trophic networks, and disturbance dynamics, such as fires. In some cases and under certain conditions, changes driven by invasive species can be irreversible and result in local extinctions of native species or radical changes in ecosystem functioning. However, there is currently limited availability of quantitative studies on the impacts of most invasive species, and it has been recognized that knowledge in this area is still limited in breadth and depth.
In the national context, it is of great importance to understand the impacts that invasive species can have on ecosystems, mainly because the central Chile biodiversity hotspot (between 25 and 47ºS) has high levels of endemism, in addition to the highest richness of exotic species. Added to this are other threats s such as land use change, habitat fragmentation, disturbances, and biodiversity loss.
From the perspective of basic and applied science and its transfer with development purposes, there are still significant challenges for researchers and natural resource managers focused on biological invasions. These challenges include deepening the description of invasion patterns, understanding ecological processes and biotic interactions involved in invasion processes, incorporating experimental studies to assess the impacts of invasions, and integrating them with conservation and ecosystem restoration studies at the landscape scale.
Regarding invasive plants, recent studies indicate that 3.9% of the world’s flora (13,168 species) has become naturalized in places different from their natural distribution ranges, with potential ecological, economic, and social impacts. Invasive plants are currently ubiquitous components in many ecosystems, threatening their biodiversity. Therefore, it is relevant to properly understand and comprehend the impacts of invasive plants in order to implement environmental management strategies to prevent their introduction, control their spread, and progress in their eradication.
In the central-southern region of Chile, the majority of invasive flora, fauna, and fungi species are causing economic losses in productive systems, in addition to posing a complex threat to biodiversity conservation initiatives. According to the Invasive Species Specialist Group (ISSG) of the International Union for Conservation of Nature (IUCN), Chile is home to 25 out of the 100 most harmful invasive species in the world, classified based on their impacts on biological diversity, representing exemplary cases of invasions. Some relevant examples include gorse (Ulex europaeus), brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), domestic cat (Felis catus), wild boar (Sus scrofa), rabbit (Oryctolagus cuniculus), and red deer (Cervus elephus).
Furthermore, there is a significant presence of other invasive species that are causing impacts, such as the european hare (Lepus europaeus), american beaver (Castor canadensis), american mink (Neovison vison), yellow jacket wasp (Vespula germanica), european bumblebee (Bombus terrestris), blackberrys (Rubus ulmifolius and R. constrictus), several pine species (Pinus contorta, P. radiata, Pseudotsuga mensiezii), sweetbriar (Rosa rubiginosa), silver wattle tree (Acacia dealbata), and french broom (Teline monspessulana).
In conclusion, to mitigate the multiple impacts of biological invasions, it is important to prevent the introduction and spread of invasive species. In this regard, measures such as early detection and swift removal of invasive species found in the field, regulation of exotic species trade, and public education about invasive species and their impacts on native biodiversity are necessary.