Midwest forests provide numerous economic and ecological benefits, yet threats from a changing climate are interacting with existing stressors such as invasive species and pests to increase tree mortality and reduce forest productivity (likely, high confidence). Without adaptive actions, these interactions will result in the loss of economically and culturally important tree species such as paper birch and black ash (very likely, very high confidence) and are expected to lead to the conversion of some forests to other forest types (likely, high confidence) or even to non-forested ecosystems by the end of the century (as likely as not, medium confidence). Land managers are beginning to manage risk in forests by increasing diversity and selecting for tree species adapted to a range of projected conditions.

This finding is from chapter 21 of Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II.

Process for developing key messages:

The chapter lead authors were identified in October 2016, and the author team was recruited in October and November 2016. Authors were selected for their interest and expertise in areas critical to the Midwest with an eye on diversity in expertise, level of experience, and gender. The writing team engaged in conference calls starting in December 2016, and calls continued on a regular basis to discuss technical and logistical issues related to the chapter. The Midwest chapter hosted an engagement workshop on March 1, 2017, with the hub in Chicago and satellite meetings in Iowa, Indiana, Michigan, and Wisconsin. The authors also considered other outreach with stakeholders, inputs provided in the public call for technical material, and incorporated the available recent scientific literature to write the chapter. Additional technical authors were added as needed to fill in the gaps in knowledge.

Discussion amongst the team members, along with reference to the Third National Climate Assessment and conversations with stakeholders, led to the development of six Key Messages based on key economic activities, ecology, human health, and the vulnerability of communities. In addition, care was taken to consider the concerns of tribal nations in the northern states of the Midwest. The Great Lakes were singled out as a special case study based on the feedback of the engagement workshop and the interests of other regional and sector chapters.

Note on regional modeling uncertainties

Interaction between the lakes and the atmosphere in the Great Lakes region (e.g., through ice cover, evaporation rates, moisture transport, and modified pressure gradients) is crucial to simulating the region’s future climate (i.e., changes in lake levels or regional precipitation patterns).fe83e7d3-3f29-4aef-81ae-28abd70dda2e^,94a4d51e-96a4-4155-926d-31be60e2206a Globally recognized modeling efforts (i.e., the Coupled Model Intercomparison Project, or CMIP) do not include a realistic representation of the Great Lakes, simulating the influence of the lakes poorly or not at all.9db319af-7cec-440e-8dda-41526fed6cd0^,5295673e-703b-42f8-9792-4ccf8e3cf747^,03f91fdd-6d7d-431b-997b-91f63f52fe45^,ee7f8311-bd00-4353-87a9-61ffb7813bf0^,1cd8ac44-e9d5-4a2e-ab8e-e48c8988bbc2 Ongoing work to provide evaluation, analysis, and guidance for the Great Lakes region includes comparing this regional model data to commonly used global climate model data (CMIP) that are the basis of many products practitioners currently use (i.e., NCA, IPCC, NOAA State Climate Summaries). To address these challenges, a community of regional modeling experts are working to configure and utilize more sophisticated climate models that more accurately represent the Great Lakes’ lake–land–atmosphere system to enhance the understanding of uncertainty to inform better regional decision-making capacity (see http://glisa.umich.edu/projects/great-lakes-ensemble for more information).

Description of evidence base:

Multiple ecosystem vulnerability assessments that have been conducted for major forested ecoregions within the Midwest8b4159ec-1edb-4fab-8af5-10a8cdec8fb5^,ecc6f6d0-d7af-4bfc-b6cd-f60d2eb3f200^,8c05015c-4269-4b25-86e0-2d45df89613d^,b76e2693-17a0-4075-b40f-6440a89d7040^,8f9b5614-e7c7-480b-acc8-962a89effaa0 suggest that climate change is expected to have significant direct impacts to forests through effects of warming and changes in the timing and amounts of precipitation.f5c3df5e-c125-4179-b646-e073ad3c5bc9^,62b16439-014f-4a7a-9b2f-33d475e29f56^,156c6133-407b-4462-8e60-3a1824be3479^,71a27619-b62e-4138-8727-9ade35b81a60

Significant indirect impacts to forests are expected as warming increases the negative effects of invasive plants, insect pests, and tree pathogens of forests.98e8338c-3c49-49f7-9334-d4c28a901ad0^,176185dd-5730-4b29-97b4-427d3dccfe84 Increasing stress on individual trees from climate changes (warming temperatures, drought, and frost damage) increases the susceptibility of trees to the impacts from invasive plants, insect pests, and disease agents.b3ba546e-9bbf-47c2-a9da-3ddc4252561c^,e2bfdf4e-c37c-4b33-9370-fc6db9166d4f

Direct and indirect impacts of climate change may lead to the decline of culturally7e39f05f-d63f-473a-87c3-93d733ea178b^,debdf209-4050-4706-965c-09cff7ec353b and economically important tree species,b4bcfb86-ffa2-4d7c-9a26-2927804b09a0 as well as leading to shifts in major forest types and altered forest composition as tree species at the northern limits of their ranges decline and southern species experience increasing suitable habitat.e3a1fd13-e8f9-4f15-a31c-ad6c2613e685 These shifts raise the possibility of future losses of economic and cultural benefits of forests due to conversion to different forest types or the change to non-forest ecosystems.3def47b9-0e32-440b-bef1-f9bc176a7dd0^,6b72f67d-2b83-44a1-b89c-d2dffc5d6099^,ec2a899f-9470-47d9-8f2f-4d02663e68d5

Many examples of land managers implementing climate adaptation in forest management exist, suggesting significant willingness to address the impacts of a changing climate across diverse land ownerships in managed forests7242780c-93ee-4a39-9505-d0bd2f67c62b and urban forests.6352c444-c49b-4dac-b375-2b72b8532ebe Forest management strategies to adapt to a changing climate highlight the importance of increasing forest diversity and managing for tree species adapted to a range of climate conditions.28ab77d2-73c7-4554-82ef-c8bd5e095887 The importance of Traditional Ecological Knowledge for informing approaches for climate adaptation on tribal lands and within ceded territory is recognized.44b1444b-29ab-4edd-b285-f8820660fc32

New information and remaining uncertainties:

There is significant uncertainty surrounding the ability of tree species migration rates to keep pace with changes in climate (based on temperature and precipitation) due to existing forest fragmentation and loss of habitat. Uncertainty in forest management responses, including active and widespread adaptation efforts that alter forest composition, add to the uncertainty of tree species movements. This leads to considerable uncertainty in the extent to which shifts in tree species ranges may lead to altered forest composition or loss of forest ecosystems in the future.

Due to the complex interactions among species, there is uncertainty in the extent that longer growing seasons, warming temperatures, and increased CO₂ concentrations will benefit tree species, due to both limitations in available water and nutrients, as well as limited benefits for trees relative to the positive influences of these changes on stressors (invasives, insect pests, pathogens).

Assessment of confidence based on evidence:

There is high confidence that the interactions of warming temperatures, precipitation changes, and drought with insect pests, invasive plants, and tree pathogens will likely lead to increased tree mortality of some species, reducing productivity of some forests. There is very high confidence that these interactions will very likely result in the decline of some economically or culturally important tree species. Additionally, there is high confidence that suitable habitat conditions for tree species will change as temperatures increase and precipitation patterns change, making it likely that forest composition will be altered and forest ecosystems may shift to new forest types. Due to uncertainties on species migration rates and forest management responses to climate changes, there is medium confidence that by the end of the century, some forest ecosystems are as likely as not to convert to non-forest ecosystems.

Provenance

This finding was derived from scenario rcp_4_5
This finding was derived from scenario rcp_8_5