PORTLAND ” Global warming is likely to greatly increase spending on fighting wildfires and greatly reduce salmon habitat in the Northwest, two new reports suggest.

The University of Oregon’s Institute for a Sustainable Environment projects that an average wildfire year for Oregon in the 2020s will see 50 percent more acres of forest burned than during the 20th century. By the 2040s the increase will be 100 percent.

Thinning forests may reduce the severity of wildfires, but not the frequency, and annual state spending to fight wildfires is likely to increase from the current range of $40 million to $64 million to, in inflation-adjusted dollars, $60 million to $96 million in the 2020s and $80 million to $128 million in the 2040s, the report said.

The report estimated federal spending to fight wildfires in Oregon would rise from current range of $20 million to $132 million a year to, in inflation-adjusted dollars, $30 million to $197 million a year in the 2020s and $40 million to $263 million in the 2040s.

In another report, a panel of 11 independent scientists told the Northwest Power Planning Council that temperatures in the Northwest have already gone up nearly 2 degrees Fahrenheit since 1900, which is 50 percent more than the global average. The increase is expected to continue at a rate of about 1 degree Fahrenheit each decade.

The amount of precipitation over the Northwest is expected to remain about the same, but more will fall as rain and less as snow, making for higher winter river flows and warmer water temperatures ” too warm for salmon in some places.

The report notes some studies expect more than 40 percent of rivers in Oregon and Idaho will be too warm for salmon by the year 2090, and 22 percent in Washington. It would be even worse for bull trout, which demand even colder water.

Warmer water makes salmon eggs hatch quicker, producing smaller juvenile fish that are more likely to be eaten by predators. Warmer water favors fish that eat young salmon. Warmer water will also weaken adult salmon as they swim up fish ladders going over the dams, and make them more vulnerable to parasites and diseases. Warmer oceans may mean less food for salmon as they mature.

The scientists suggest that only global strategies that reduce greenhouse gases will completely address the problems, but the federal hydroelectric dams can help by releasing more cold water from reservoirs during salmon migrations and installing weirs that help young fish pass over the dams more quickly while migrating downstream.

They also suggest opening up more backwaters and sloughs along rivers to cool temperatures, protecting cold-water spawning areas, increasing control of predators such as the northern pike minnow, and considering trucks and barges to carry adult salmon up the lower Snake River in late summer when the water can be lethally warm.