Bioscience Evidence 2024, Vol.14, No.4, 172-183 http://bioscipublisher.com/index.php/be 173 2 Historical Context 2.1 Beavers in prehistoric and early historical times Beavers have long been recognized as significant ecosystem engineers, with their activities dating back to prehistoric times. Historical and stratigraphic records suggest that hundreds of millions of beavers once modified small to medium rivers throughout the northern hemisphere (Wohl, 2020). Their dam-building activities created diverse habitats, which increased biodiversity and ecosystem resilience. The Eurasian beaver (Castor fiber) and the North American beaver (Castor canadensis) have both played crucial roles in shaping riverine landscapes through their engineering activities (Brazier et al., 2020; Larsen et al., 2021). 2.2 Impact of human activities on beaver populations The beaver populations faced severe declines due to extensive hunting and habitat destruction. In Medieval times, the Eurasian beaver underwent a significant decline due to habitat loss and hunting pressures (Falaschi et al., 2023). Similarly, in North America, commercial trapping and habitat modification led to a drastic reduction in beaver populations (Wohl, 2020). The cumulative effects of these human activities greatly diminished the ecosystem services provided by beavers, such as increased habitat diversity and nutrient cycling (Nummi et al., 2019; Wohl, 2020). 2.3 Conservation efforts and the resurgence of beaver populations In recent decades, concerted conservation efforts have led to the resurgence of beaver populations in both Europe and North America. Legal protections and reintroduction programs have been pivotal in this recovery. For instance, the Eurasian beaver population in Europe has rebounded to over 1.5 million individuals due to reintroduction efforts and natural expansion (Brazier et al., 2020). Similarly, contemporary efforts in North America have focused on reintroducing beavers and mimicking their engineering effects through beaver dam analogues (Wohl, 2020). These initiatives have not only facilitated the recovery of beaver populations but also enhanced biodiversity and ecosystem functions (Orazi et al., 2022; Treves and Comino, 2023). The resurgence of beaver populations has prompted a re-evaluation of their role in ecosystem management. Beavers are now recognized for their potential to provide ecosystem services, such as natural flood management and biodiversity conservation (Figure 1) (Puttock et al., 2021). However, their activities can also lead to human-wildlife conflicts, necessitating balanced management approaches (Falaschi et al., 2023; Treves and Comino, 2023). As beaver populations continue to expand, understanding their ecological impacts and developing effective management strategies will be crucial for maximizing their benefits while minimizing conflicts (Nummi et al., 2019; Brazier et al., 2020; Larsen et al., 2021). 3 Beaver Biology and Behavior 3.1 Anatomy and physiology of beavers Beavers, belonging to the genus Castor, are highly specialized rodents known for their significant impact on ecosystems through their engineering activities. The American beaver (Castor canadensis) and the Eurasian beaver (Castor fiber) exhibit distinct anatomical and physiological traits that enable them to thrive in diverse environments. One of the key features of beavers is their cranial morphology, which is highly adapted to their foraging and feeding requirements. Studies have shown that the skull morphology of beavers is influenced by local environmental conditions such as temperature, precipitation, biomass, and tree hardness, which affect the functional traits of their masticatory system (Diamond et al., 2023). This local adaptation highlights the beaver's ability to modify its phenotype in response to changing environmental conditions, ensuring its survival and efficiency as an ecosystem engineer. 3.2 Social structure and behavior Beavers are known for their complex social structures and behaviors, which play a crucial role in their ability to modify and manage ecosystems. They live in family units called colonies, typically consisting of a monogamous pair and their offspring from the current and previous years. This social structure facilitates the construction and maintenance of dams and lodges, which are essential for their survival and ecological impact. Beavers are also
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