Seasonal change is important to consider when managing conservation areas at landscape-scales. The study of such patterns throughout the year is referred to as phenology. Recurring life-cycle events that are initiated and driven by environmental factors include animal migration and plant flowering. Phenological events, such as fall color change in deciduous forests, the first flowering in spring, and for those with allergies, the start of the pollen season, capture public attention. These events can impact our daily lives, provide clues to help understand and manage ecosystems, and provide evidence of how climate variability can impact the natural cycle of plants and animals. Phenological observations can be gathered at a range of scales from plots smaller than an acre to landscapes of hundreds to thousands of acres. Linking these observations to diverse disciplines such as evolutionary biology or climate sciences can help further research in species and ecosystem responses to climate change scenarios at appropriate scales.
A cooperative study between the National Park Service, the US Geological Survey and NASA has been exploring how satellite information can be used to summarize phenological patterns observed at the park, or landscape scale and how those summaries can be presented to both park managers and visitors. This study specifically addressed seasonal changes in plants, including the onset of growth, photosynthesis in the spring, and the senescence of deciduous vegetation in the fall. The primary objective of the work is to demonstrate that seasonality even in protected areas change considerably across years. A major challenge is to decouple natural variability from possible trends – directional change that can lead to a permanent and radically different ecosystem state. Trends can be both a gradual degradation of the landscape (often from external influences) or steady improvement (by implementing long-term conservation plans). In either case, it is important to first grasp the magnitude of natural variation so that it is not confused with actual trends.
This work used existing and freely available remote sensing data, specifically the NASA-funded 250 meter spatial resolution land-surface phenology product for North America. This product is calculated from an annual record of vegetation health observed by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The land surface phenology product is, in essence, a method to summarize all the observations throughout a year into a few, key, ecologically relevant “metrics”.
