Reading 4 Flashcards
how has the elimination of some forest fires contributed to the mountain pine beetle problem in British Columbia?
efforts to suppress forest fires have led to unnaturally dense forests, making them prime targets for mountain pine beetles.
what is the reason that some scientists believe that the beetle could potentially spread all the way to the Atlantic provinces of Canada?
the beetle is already in jack pines. It has now colonized Alberta all the way east to Saskatchewan and north to the Yukon and Northwest Territories. – these Jackpines live as far east as Nova Scotia
Rising temperatures and drought have stressed trees, leaving them unable to fight an invasion. Warmer weather also has boosted the beetles’ population and greatly expanded their range.
in the past, the relationship between beetles and the forest was considered mutually beneficial. explain how that has changed in recent years.
the beetles were native insects and typically lived in small numbers and killed only a few trees. their activity was part of the natural cycle: occasional population booms would kill swaths of trees in a single region, but this helped maintain forest health by thinning out older or weaker trees and creating space for new growth
recently, this balance has been lost. tens of millions of acres of forest dying across vast regions, not just isolated areas.
factors like fire suppression (leading to unnaturally dense forests) and climate change (causing warmer temperatures and drought-stressed trees) have allowed beetle populations to explode and spread far beyond their historical range.
describe how female beetles have evolved to survive the natural defenses that the trees produce.
originally, when a female beetle lands on a tree, she chews into the bark to assess its suitability. If the tree meets her standards, she burrows further, severing resin ducts, which are the tree’s primary defense mechanism.
the beetle has evolved to ingest the resin, surviving the tree’s attempt to flush it out. the beetle then converts the ingested resin into a pheromone. This pheromone is released into the air, signaling to other beetles that a suitable host has been found, leading to a mass attack
how has the beetle indirectly impacted water resources for both people and salmon in waterways?
in areas where forests are devastated, the unshaded snow melts faster. As a result, rivers crest earlier in the year, before the dry season when people and ecosystems need the water most.
Dead lodgepole pines lining riverbanks, like in the Yankee Fork of the Salmon River, negatively affect threatened salmon. The trees are vital for slowing snowmelt, which keeps streams cool into spring and limits excess silt.
where beetles have killed mature pines, sun melts the snowpack faster, diminishing summer water supplies.
explain what is meant by tipping an ecosystem. Why are the beetles only partly to blame for such a phenomenon?
“tipping” refers to the point at which an ecosystem undergoes a significant and potentially irreversible change in its structure and function.
mountain pine beetles are only partly to blame for the ecosystem tipping because several other factors have contributed to the severity of the outbreak: fire suppression and climate change
