Disturbing the forest: climate change and pests are leaving us with a younger forest
Summary
Climate can greatly influence the impact of biotic disturbances, such as invasive insects and pathogens, in forested ecosystems. Weed et al. (2013) identify three general mechanisms for climate to influence these disturbances: (1) climate causes changes to the abundance and distribution of the disturbance agent (insect or pathogen); (2) climate directly affects tree defenses and/or tolerance; and (3) climate alters the interactions between disturbance agents. Reviewing the scientific research on notable native and non-native forest insects (27) and diseases (22), the group found that warmer winters and warmer and drier summers were associated with higher levels of insect disturbance and that insects are particularly responsive to changes in climate in North America. In contrast, the influences of climate on forest diseases is less well defined and some diseases fared better in warmer and wetter summers and others in warmer and drier. However, both the insects and diseases studied created more widespread or intense disturbances with milder winters - indicating that climate change is making our forests more vulnerable to biotic disturbances. Weed et al. (2013) identified that many of the most impactful biotic disturbances were non-native (particularly in the Northeast), but that climate change also is increasing the emergence of native and non-native sleeper species. These disturbances, in particular intense and/or widespread disturbances, can have long term impacts on forest ecosystems, including: changes to nutrient cycling, decreases in stored carbon, changes to soil moisture and stream flow, a shift to younger forests, etc. Weed et al. (2013) also identified that the interaction of climate change and biotic disturbances presents an increasingly challenging task for forest managers: more frequent disturbances are creating a patchwork of younger forests and more rapidly shifting species, which will require new management strategies and increased collaboration across regions impacted by these disturbance agents.
Take home points
Climate change will continue to increase the intensity and breadth/spread of biotic disturbances and forest insects in particular
Biotic disturbances have long-term impacts on forest ecosystems, including influencing the cycling of nutrients, carbon, water, and energy, with direct feedbacks to the climate
As disturbances increase with climate change, the extent of mature forests, along with their unique ecosystem services, is likely to decrease
Management implications
Increased collaboration and communication between managers in different regions (as promoted and supported by RISCC!) is imperative as these new disturbances create a mismatch between disturbance types and management expertise
New management strategies are needed for the novel forest ecosystems created by forest insects and pathogens
Keywords
Forest pests, Invasive invertebrates, terrestrial habitat, Review