International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 217-228 http://ecoevopublisher.com/index.php/ijmec 22 4 Germany introduced beavers in the middle of the 20th century. Their population has grown rapidly in river basins such as the Elbe and Rhine, creating a large number of new wetland landscapes (Halley et al., 2021). For example, in Bavaria, the number of beavers has increased to approximately 20,000 over the past few decades, and both the plant and animal diversity of their habitats have improved (Orazi et al., 2022). Beavers in the UK had been extinct for hundreds of years. Since the 21st century, they have been experimentally reintroduced in Scotland and England. A five-year trial was conducted in Knapdale, Argael, Scotland. The results proved that beavers had a significant positive effect on the restoration of local wetlands and biodiversity. In 2016, the government decided to allow beavers to remain in Scotland and provide legal protection. The 10-year trial carried out on the River Otter in Devon, England, serves as an example: The beaver family has multiplied into 15 families and built a series of DAMS, significantly reducing the flood risk in the villages and towns downstream of the basin and increasing the species of birds and invertebrates inhainhading the wetlands (Campbell-Palmer et al., 2021). 6.3 Beaver engineering impacts in extreme environments (arid regions, cold regions, etc.) Beaver engineering demonstrates unique ecological roles and challenges in various extreme environments. In arid and semi-arid regions, rivers seasonally dry up and droughts occur frequently. The dam-building and water storage functions of beavers are particularly valuable. Some experiments in the arid grasslands of western North America have shown that the introduction of beavers has significantly prolonged the water surface coverage time of streams and raised the groundwater level, providing a continuous water source for plants in the riverbank zone. In states such as Nevada and Utah, streams with beaver activity maintain water flow in summer, better supporting the survival of fish and wildlife, while streams without beavers often dry up to the bottom (Thompson et al., 2021). As a result, beavers are regarded as a kind of "ecological reservoir" and "oasis" builder in arid areas. Of course, the arid environment also restricts the performance of beaver engineering - during years of drought, water shortage may cause beavers to evacuate and the dam to fail. Therefore, in such areas, people have also attempted to use artificial simulation Beaver Dam Analogues technology to assist in maintaining water flow in order to wait for the beaver population to grow and take over (Puttock et al., 2021). In high-altitude and cold regions (such as tundra and permafrost areas), beaver expansion may have negative impacts. In recent years, in the western part of Alaska within the Arctic Circle, warming has shifted the forest line northward, causing beavers to enter tundra rivers to build DAMS and form a large number of new lakes. Although this increases surface water, it accelerates the thawing of permafrost: water bodies thaw the soil, absorb heat, cause the surrounding permafrost to sink and release a large amount of stored carbon (Figure 2) (Tape et al., 2022). The extremely cold winter also limits the beaver's active period and the supply of dam-building materials. However, once the climate warms, the distribution of beavers is bound to further advance towards the polar regions and plateaus (Dewey et al., 2022). 7 Future Research Directions and Challenges 7.1 Long-term monitoring requirements in multi-scale and multi-ecosystem environments Studies have already shown many ecological effects of beaver engineering, but large knowledge gaps still exist. These gaps require monitoring across long periods and at multiple scales. Most current work looks at short-term changes, usually 5 to 10 years, while long-term effects over decades or centuries remain unclear (Halley et al., 2021). Cross-ecosystem comparisons are also limited. Beaver activities may differ in forests, plains, dry grasslands, and tundra, yet most data come from temperate forests and wetlands (Grudzinski et al., 2022). Scale is another key factor. Local impacts are often obvious, but at the basin scale, only a higher density of dams makes the changes stand out (Puttock et al., 2021). Models and remote sensing can help measure large-scale impacts, but they need calibration with field data. In the future, high-resolution satellite images may be used to trace the long-term spread of dams and wetlands (Tape et al., 2022). Monitoring should also cover different fields, including hydrology, ecology, and social and economic aspects, to create a more complete picture (Hohm et al., 2024).
RkJQdWJsaXNoZXIy MjQ4ODYzNA==