[MCN] At 50+ years old, many US dams become hazards

[Lance Olsen]

Excerpt:  Dam removal projects that will provide 
significant ecological benefits, such as the 
Nelson, are of the highest priority, says Scott. 
Another requirement is that the structure be a 
"deadbeat dam"-one that has outlived its useful 
life and has now become a hazard.

More than 14,000 such dams exist around the 
country already. By 2020, more than 70 percent of 
the U.S.'s dams will be more than 50 years old, 
with many of those soon becoming candidates for 
removal. It's a growing movement, with dozens of 
dams coming down every year. The main obstacle is 
the often high price tag of removal, which can 
run tens of millions of dollars. Yet maintaining 
old dams and retrofitting them to meet newer 
standards also comes at a cost.

http://news.nationalgeographic.com/2016/11/dam-removal-nelson-dam-matiliha-rogue-river-hewlett-foundation-open-rivers
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" 'Triage' is a dirty word in some conservation 
circles, but like many dirty words, it describes 
something common. Whether they admit it or not, 
conservationists have long had to make decisions 
about what to save.

"As more and more admit it, open discussion about 
how the decisions are best made - by 
concentrating on particular species, or 
particular places, or absolute costs, or any 
other criterion - becomes possible. Whichever 
criteria come into play, one thing remains 
constant. The decisions have to be made quickly."

Emma Marris, "What To Let Go."
NATURE November 8, 2007

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"  Š organisms have a physiological response to 
temperature, and these responses have important 
consequences Š. biological rates and times (e.g. 
metabolic rate, growth, reproduction, mortality 
and activity) vary with temperature."

Anthony I. Dell, Samraat Pawar and Van M. Savage, 
Temperature dependence of trophic interactions 
are driven by asymmetry of species responses and 
foraging strategy  Journal of Animal Ecology 2013
doi: 10.1111/1365-2656.12081

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"Whereas any one line of evidence may be weak in 
itself, a number of lines of evidence, taken 
together and found to be consistent, reinforce 
one another exponentially."

Preston Cloud and Aharon Gibor. The Oxygen Cycle. 
Scientific American, September 1970


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