Intensive forest management (IFM) practices increase wood production but concerns regarding the impacts of these practices on biodiversity remain. A recent study used moths as an indicator of biodiversity to better understand how (IFM practices, such as using herbicides to help trees grow may influence native species. Researchers found that IFM slightly reduced the number of moth species, but the effects were not as strong as expected.
The experiment collected over 12,000 moths representing 316 species. Sampling occurred in young forests treated with different levels of herbicide. The most common level of herbicide treatment used in IFM in the Pacific Northwest U.S. led to around five fewer moth species than were found in areas with no herbicide use. However, even in the most intensively treated forests, small patches of moth host plants survived. These leftover plants helped support a surprising number of moth species.
The study also revealed a more expected conclusion, that moth diversity was closely linked to plant diversity. Forests with a greater diversity of plant species had more species of moths, supporting the idea that a diverse plant community helps maintain insect diversity. Despite the link between plant and moth diversity, and markedly different plant cover between herbicide treatments, the overall number of moths did not seem to be directly affected by IFM.
Even across a gradient of IFM practices, patches of plant diversity remain and are key to preserving moth communities. By keeping even small areas of diverse vegetation, forests can continue to support moths and other insects, helping maintain the overall health of these ecosystems.