Climate Change Tree Atlas & Bird Atlas

The model inputs are pre-defined, so no user-collected data is required. For the Tree Atlas, inputs include data on current tree species distributions from the Forest Inventory and Analysis (FIA) program, as well as datasets that capture different climate, elevation, soil, and land use variables. SHIFT inputs include species abundance, landscape fragmentation, and historical migration rates. Adaptability scores are derived from nine biological and 12 disturbance factors, based on the results of a literature review. For the Bird Atlas, inputs include data on current bird distribution from the Breeding Bird Survey as well as data on climate, elevation, and tree species distributions. More information on model inputs, as well as related literature, is available on the Climate Atlas website under “Model Info” and “Frequently Asked Questions”.

Climate Atlas outputs include maps of individual species, as well as importance values (Tree Atlas), incidence (Bird Atlas), and statistical summaries of predictor variables for a species. For the Tree Atlas, there are regional tables that summarize current and potential future habitat, capability, and migration potential for multiple tree species. Tables are available at a variety of scales for current and potential tree species in a region.

Importance value is a measure of abundance that accounts for both tree basal area and number of stems, ranging from 0 - 100. Incidence is calculated from the number of years (from 1981-1990) that a species was observed on the Breeding Bird Survey routes selected by the USGS. Incidence value ranges from 0 to 1.

Each Atlas should be used at an appropriate scale – the Bird Atlas analyses are conducted at a 20x20 km cell scale, while Tree Atlas analyses are run using a hybrid scale of either a 10x10 or 20x20 km cell. It is recommended that at least 8000 sq. km (3088 sq. mi) be used to appropriately interpret model outputs. Additionally, it is important to consider that modeling comes with some level of uncertainty and limitations. Different climate model and emissions scenarios produce a range of projected future climate conditions. The Climate Atlas addresses this uncertainty by providing outputs for species under several climate models and emissions scenarios, creating outcomes that reflect potential species distributions under a range of future conditions.

The Atlas also provides model reliability rankings for habitat suitability, as DISTRIB-II generates better models for some species over others due to factors such as species rarity, sampling abundance, and geographic area occupied by a species. Reliability rankings are based on the statistical techniques used to create the model, and essentially account for the strength of model variables in predicting a species location. Projections for species with low model reliability should be interpreted with caution.

DISTRIB-II only predicts where a species suitable habitat may exist under future conditions, it does not predict a species future location. The combination of DISTRIB-II and SHIFT creates an output that characterizes both habitat quality and the likelihood that a propagule will reach a site. It does not assess whether successful establishment and maturation will occur. Finally, there are many local factors not captured in the model that may influence a species’ success at a site, including factors such as land use change, genetics, competition with other species, and forest pests.

Before using the Climate Change Atlas tool, it is best to read the “Cautions”, “Model Info”, and “FAQ” sections on the Atlas website to understand the appropriate uses and limitations more fully.

Researchers at the USDA Forest Service Northern Research Station (NRS) first developed a statistical model in 1996 to assess potential changes in habitat for common tree species in the eastern United States. Since then, the model has gone through several improvements, leading to the development of the DISTRIB model which is the basis for the Climate Change Atlas. A list of relevant publications may be found on the Climate Change Atlas website under “Model Info”.