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Climate change in southeast Alaska


Climate change in southeast Alaska are changes which occur in southeast Alaska as average temperatures rise as a result of global warming.

The temperate rainforest that covers this area is a result of humid summers and transient snow cover in winter. The conifers that thrive in this moist climate are free from fire risk as compared to the forests to both the north and south.

Warmer weather will lengthen the growing period of the trees and the increase in evapotranspiration is likely to outweigh the increase of precipitation. Assuming a scenario involving a mid-range increase in emissions, the average temperature may rise by about 3 °F by the year 2040 and by 6 °F by 2080. The trees will grow more vigorously but fungi that cause rot will also thrive, there is likely to be an increase in windthrow, and fire risk may rise.

With winter temperatures increasing, the type of precipitation will change. Lack of snow cover on the ground will expose tree roots to colder soils, and yellow ceder is already showing the result of this with many trees dying. The melting of glaciers in the watershed is likely to accelerate and will cause hydrological changes that will impact the wetland habitats and the distribution of wildlife. Animals such as the black-tailed deer, moose and mountain goat may benefit from less snow cover, while such mammals as the northwestern deer mouse that tunnels under the snow are likely to be disadvantaged.

The temperate rainforest in southeast Alaska, in the Tongass National Forest is a perhumid (always wet) temperate rain forest. A perhumid temperate rainforest is a rainforest that receives above ten percent of its annual rainfall during the summer. Another contributing factor to define a perhumid rainforest is transient snow must be present in the winter with mean annual temperatures of 7 °C. These qualities define the rain forest as cool and temperate.

At present, the southeast Alaskan temperate rainforest is strongly dominated by old growth stands. The vegetation is strongly represented by a series of conifers; Sitka spruce, western hemlock, mountain hemlock, amabilis fir, shore pine, western red cedar and Alaska yellow cedar. This forest, unlike its neighboring regions to the north and south, is completely safe from fires. Fire is virtually nonexistent in the southeast region due to the moist and cool climate. Small scale windthrow is the main disturbance that affects the rain forest in this region. Temperatures and precipitation in the southeast region of Alaska for the year of 2011 have matched what a typical temperate rainforest needs to be defined as one by DellaSala. Juneau, Alaska, received 66.40 inches of precipitation and averaged 40.6 °F during 2011. Snowfall, as will be discussed in further detail later, is an important player for the temperate rainforest in this region, and the Juneau area received 115.9 inches which, converted to its liquid equivalent is 11.59 inches. The weather characteristics of the southeast region match up very well with what a temperate rainforest needs as defined by DellaSala.


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