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CORVALLIS, Ore. - The Northwest is facing increased risks from the decline of forest health, earlier snowmelt leading to low summer stream flows, and an array of issues facing the coastal region, according to a new climate assessment report.

Written by a team of scientists coordinated by the Oregon Climate Change Research Institute (OCCRI) at Oregon State University, the report is the first regional climate assessment released since 1999. Both the 1999 report and the 2013 version were produced as part of the U.S. National Climate Assessment; both Washington and Oregon produced state-level reports in 2009 and 2010.

OSU's Philip Mote, director of the institute and one of three editors of the 270-page report (as well as the 1999 report), said the document incorporates a lot of new science as well as some additional dimensions - including the impact of climate change on human health and tribal issues. A summary of the report is available online at: http://occri.net/reports

Amy Snover, director of the Climate Impacts Group at the University of Washington, said there are a number of issues facing the Northwest as a result of climate change.

"As we looked across both economic and ecological dimensions, the three that stood out were less snow, more wildfires and challenges to the coastal environment and infrastructure," said Snover, who is one of the editors on the report.

The report outlines how these three issues are affected by climate change.

"Studies are showing that snowmelt is occurring earlier and earlier and that is leading to a decline in stream flows in summer," Mote said. "Northwest forests are facing a huge increase in wildfires, disease and other disturbances that are both direct and indirect results of climate change. And coastal issues are mounting and varied, from sea level rise and inundation, to ocean acidification. Increased wave heights in recent decades also threaten coastal dwellings, roads and other infrastructure."

OCCRI's Meghan Dalton, lead editor on the report, notes that 2,800 miles of coastal roads are in the 100-year floodplain and some highways may face inundation with just two feet of sea level rise. Sea levels are expected to rise as much as 56 inches, or nearly five feet, by the year 2100.

Earlier snowmelt is a significant concern in the Northwest, where reservoir systems are utilized to maximize water storage. But, Dalton said, the Columbia River basin has a storage capacity that is smaller than its annual flow volume and is "ill-equipped to handle the projected shift to earlier snowmelt...and will likely be forced to pass much of these earlier flows out of the system."

The earlier peak stream flow may significantly reduce summer hydroelectric power production, and slightly increase winter power production.

The report was funded by the National Oceanic and Atmospheric Administration, through the Oregon Legislature's support of the Oregon Climate Change Research Institute at OSU, and by in-kind contributions from the authors' institutions.

Mote said new research has led to improved climate models, which suggest that the Northwest will warm by a range of three to 14 degrees (Fahrenheit) by the year 2100. "The lower range will only be possible if greenhouse gas emissions are significantly reduced." In contrast, the Northwest warmed by 1.3 degrees from the period of 1895 to 2011.

Future precipitation is harder to project, the report notes, with models forecasting a range from a 10 percent decrease to an 18 percent increase by 2100. Most models do suggest that more precipitation will fall as rain and earlier snowmelt will change river flow patterns.

That could be an issue for agriculture in the future as the "Northwest's diverse crops depend on adequate water supplies and temperature ranges, which are projected to change during the 21st century," the report notes. Pinpointing the impacts on agriculture will be difficult, said Sanford Eigenbrode of the University of Idaho, another co-author.

"As carbon dioxide levels rise, yields will increase for some plants, and more rainfall in winter could mean wetter soils in the spring, benefitting some crops," Eigenbrode pointed out. "Those same conditions could adversely affect other crops. It is very difficult to say how changing climate will affect agriculture overall in the Northwest, but we can say that the availability of summer water will be a concern."

Mote said there may be additional variables affecting agriculture, such what impacts the changing climate has on pests, diseases and invasive species.

"However, the agricultural sector is resilient and can respond more quickly to new conditions than some other sectors like forestry, where it takes 40 years or longer for trees to reach a harvestable age," noted Mote, who is a professor in OSU's College of Earth, Ocean, and Atmospheric Sciences.

The Northwest has not to date been vulnerable to many climate-related health risks, the report notes, but impacts of climate change in the future are more likely to be negative than positive. Concerns include increased morbidity and mortality from heat-related illness, air pollution and allergenic disease, and the emergence of infectious diseases.

"In Oregon, one study showed that each 10-degree (F) increase in daily maximum temperature was associated with a nearly three-fold increase of heat-related illness," said Jeff Bethel, an assistant professor in the College of Public Health and Human Sciences at OSU and one of the co-authors of the report. "The threshold for triggering heat-related illness - especially among the elderly - isn't much."

Northwest tribes may face a greater impact from climate change because of their reliance on natural resources. Fish, shellfish, game and plant species could be adversely affected by a warming climate, resulting in a multitude of impacts.

"When tribes ceded their lands and were restricted to small areas, it resulted in a loss of access to many species that lived there," said Kathy Lynn, coordinator of the Tribal Climate Change Project at the University of Oregon and a co-author of the report. "Climate change may further reduce the abundance of resources. That carries a profound cultural significance far beyond what we can document from an economic standpoint."

Snover said that the climate changes projected for the coming decades mean that many of the assumptions "inherent in decisions, infrastructure and policies - where to build, what to grow where, and how to manage variable water sources to meet multiple needs - will become increasingly incorrect.

"Whether the ultimate consequences of the climate impacts outlined in this report are severe or mild depends in part on how well we prepare our communities, economies and natural systems for the changes we know are coming," Snover said.

Other lead co-authors on the report are Rick Raymondi, Idaho Department of Water Resources; W. Spencer Reeder, Cascadia Consulting Group; Patty Glick, National Wildlife Federation; Susan Capalbo, OSU; and Jeremy Littell, U.S. Geological Survey.