Temperature is an important factor governing when seasonal events happen in many plant and animal species. For many species, events like leaf-out, flowering, and egg hatch are triggered when a specific amount of heat has accumulated since the start of the year. We typically measure accumulated heat in growing degree days (GDDs). The Thermal Calendars tool indicates when particular GDD levels (or thresholds) of accumulated warmth are met each year in the northeastern U.S. Local resource managers can use the tool to determine when problematic insect pests are expected to enter particular life stages when they may cause the most damage or are most readily controlled.

Global temperatures are increasing and the impacts are numerous and wide ranging. Temperatures have been rising at a particularly fast rate in the northeastern U.S., including many densely populated areas like New Jersey. To document environmental changes and better understand the impacts of climate change in this region since the mid-1960s, researchers gathered data on sea and air temperatures, lake ice, and snowfall. They complimented the weather data with observations of spring leaf-out and flowering in local lilac plants. The researchers found clear evidence of climate change, with notable increases in both daytime and nighttime temperatures and earlier spring plant activity. These changes will have numerous economic, social, and ecological impacts. Among other effects, earlier spring onset has the potential to alter plant-pollinator interactions and the length of the pollen and growing seasons.

Insect pests, like emerald ash borers and spongy moths, pose a significant threat to forests in North America. Management of these pests depends on information about which trees are at greatest risk and which treatments are likely to be most effective. Outbreaks of spruce budworm can devastate fir and spruce forests in the northeastern U.S. and Canada, but the risk to other tree species has not been well documented. Researchers in Maine used Nature’s Notebook observations and tree ring data to show that spruce budworms also feed on eastern hemlock trees, which leaf out at the same time as fir and spruce trees. Understanding the risk to eastern hemlock trees is important because the trees play a unique role in eastern forests and are also harvested commercially.

Results from many small-scale studies have shown that warming temperatures are causing plants to leaf-out and flower earlier than they have in the past. However, it has been difficult to know whether these patterns hold true for a wide variety of plant species at a continental scale. To answer this question, researchers used thousands of observations of plants in the eastern U.S. that were submitted to Nature’s Notebook, mainly by volunteers. They found that leaf-out and flowering occurred earlier with warmer temperatures, but the effects varied among species and locations. Invasive species, shrub species, and species at southern latitudes were more sensitive to warming temperatures than other species. These patterns were similar to results from analyses of data collected by professionals and consistent with results from previous scientific studies, demonstrating the value of Nature’s Notebook observations.

As the world becomes increasingly urban, it will become more important to maintain diverse plant communities in and around cities. A diverse plant community provides many benefits to people and wildlife inhabiting urban areas. In many cities, we have incomplete information about plant species and distributions. So, researchers gathered data from published scientific papers, unpublished reports, and observations submitted to community science programs like USA-NPN’s Nature’s Notebook to see whether combining information from all these sources provided a more complete picture of urban plant biodiversity. They compiled more than 171,000 observations of plants in the Chicago, Illinois area and documented more than 2,200 plant species. Community science programs contributed more observations of more plant species in more diverse locations than scientific studies or reports. However, professional scientists documented a significant number of native species with limited distributions that were not observed by community scientists. In all, the study highlighted the value in combining different types of data to better characterize and manage plant communities in urban areas.

As the climate changes, there has been a significant increase in the frequency of extreme weather events like heat waves, droughts, and hurricanes. We know that increases in average temperatures affect the timing of plant and animal activities, but the effects of extreme weather events are largely unknown. To address this knowledge gap, researchers used millions of photos of plants, butterflies, and moths that were submitted to iNaturalist between 2016 and 2022 to evaluate the effects of extreme heat, cold, dry, or wet conditions on the timing of plant flowering and adult insect activity. The results showed that the onset and duration of plant and animal activities were impacted by extreme events and not just changes in average climate conditions. However, the effects of extreme weather were complex, often differing between plants and animals and varying regionally. Results from this study can help us predict how plant and insect populations will respond to extreme weather events, which are likely to occur more often with climate change.