Notes for Lecture #13:

        Mt Graham

        Copyright 1996. May not be reproduced for commerical purposes

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        Mt Graham

        The complex of the high peaks (High, Emerald, Hawk, Heliograph peaks) of the Pinalenos mountains of SE Arizona

        View of the Mt. Graham observatory complex. From left-right: VAT telescope, SMT telescope (north of SMT = maintance blgd), far right, cleared site for LBT. Scale: cleared LBT site = 1.6 arces, total footprint here is around four acres.

        The Mt. Graham red squirrel

        		 Tamiasciurus hudsonicus grahemensis

      • Collects /stores cones (spruce, douglas fir,..), & mushrooms

      • Middens = food storage structures, garbage dumps

        		• The red squirrel has an extremely wide range in North America, with more than 30 named subspecies. The Mt. Graham subspecies was namely primarily because of its assumed isolation from other populations. Phenotypically, it is not distinquishable for other nearby populations.

        Criteria used to examine impact of proposed observatory

        Taking

      • is assumed to occur if any clearing occurs with 75 meters of a midden, it as assumed lost, and the squirrel with it.

        • By this standard, one squirrel is lost

        • This is very likely an overestimate

        Direct habitat loss

      • Habitat is rated by quality. The highest quality habitat supports 0.15 middens (= squirrels)/acre

      • Project clears roughly 6 acres

      • IMPACT: assuming all 6 cleared acres in highest quality habitat gives 6 * 0.15 = 0.9 squirrel-supporting habitat lost

        • Hence, the total potential capacity for squirrels is reduced by 1.

        Edge effects

      • Cleared edges can degrade the forest

      • Conservative effect (OVERESTIMATES impact): Assume a factor of 4, giving impact as 6*4 = 24 acres. Roughly half of this is through habitat rated as very poor to unsuitable squirrel habitat, giving 12 acres

        • effect is 12 * 0.15 = 1.8 squirrel-supporting habitat lost

        • Hence, the total potential capacity for squirrels is reduced by 2.

        Is all habitat equally important?

        		Life zones on Mt. Graham

        Assumption of the Biological Option: The Spruce-fir forest is a refugium

        When population size is low, the bulk of the population is assumed to reside in the spruce-fir, increasing the importance of this region

        Running the Numbers

      • Thus, worst-case from data

        • Loss in the carrying capacity of 2 squirrels

        • Direct loss of one squirrel through taking

        • Magnification factor: spruce-fir refugium

        What effect does this have?

      • Computer simulations to examine how these losses change the probability of extinction

        The above figure shows the probability of extinction (p) as a function of population size N. Hence, to compute the impact of the project, one simply computes the effect of the project on N and then finds the change in probablity of extinction p. For example, if the project reduces carrying capacity by x, then compare p for N and (N-x).

        The increase in probability of extinction assuming a loss of 2 (blue dots) or 5 (white dots) squirrels, as a function of population size

        What the current situtation?

        Construction began in 1989

        Squirrel numbers have significantly increased since construction

        Mixed conifer habitat is more important than spruce fir habitat

        When rare, most of the population is found in mixed conifer.

        Squirrel densities (per acre) in Spruce-fir vs. mixed conifer

        Mixed ConiferSpruce fir
        19840.150.12
        19890.100.02

      • Note in the figure below that the bulk of the popualton (> 50 %) is in mixed conifer. Further, the fraction in mixed conifer is highest when the population is smallest (e.g., 1990)

        Additional evidence for importance of mixed-conifer habitat

        Hoffmeister (Mammals of Arizona 1986, Table 4.1) gives habitat sightings for all red squirrels in Arizona as

        Montane conifer forests83.8%
        Spruce-Alpine fir forests16.2%

        Current data vs. that assumed in original biological opinion

        Given these data, what is the most reasonable estimates of impact?

      • More realistic measure of edge effects gives total acres impacted at 12, over half of which is in very poor-unsuitable habitat.

        • Total impact = 6 acres

        When population size large (exceeding 250)

      • Since all in spruce-fir, density is less than 0.2 squirrels/acre giving

        • 6 * 0.2 = 1.2 squirrels

        • Increase in probability of extinction less than 0.1 percent

        When population size is small (150)

      • density in spruce-fir greatly declines

        • Assuming density = 0.05

          • 6*0.05 = 0.3 squirrels

          • increase in probability of extinction less than 0.08 percent

        • Assuming density = 0.02

          • 6*0.02 = 0.12 squirrels

          • increase in probability of extinction less than 0.03 percent

        Hence, impact is least when population is smallest

        Maximal impact is an increases in the probability of extinction by 1/10 of one percent.

        Lastest (biologically-related) legal battle

      • The head of the squirrel monitoring team requested that the site for the LBT be moved about 300 yards to further reduce impacts

        • Telescope opponents groups sued to prevent this

        As the following midden map shows, there is squirrel activity around the originally-proposed LBT site (LBT-RPAS). Here the notation x/y means x active middens and a total of y middens. Converesely, in over 8 years of monitoring, no squirrel middens have been found near the new site (LBT-10477).

        Following approval by both the US Forest and Fish and Wildlife Services, the new 1.6 acre site was cleared in Dec 1993. This cleared site has sat vacant since then due to court actions.

        What one of the judges said

        A student asked why the courts allowed the project to be stopped. Here are the comments from the Circuit Judge Hall, the dissenting judge (the court ruled 2-1 for further studies):

        This appeal gives rise to the fifth published opinion from this Court addressing legal challenges to the construction of the Mt. Graham International Observatory. I find this fact remarkable in light of Congress's recognition in 1988 ... to insure the "immediacy of construction to the first three telescopes." ... I find the further delay imposed by today's decision especially regrettable in light of the fact that the FS [US Forest Service] appears to have chosen to locate the LBT on Peak 10,477 in good faith and for laudable reasons: Peak 10,477, according to the FWS [US Fish and Wildife Service] , is now the location that would cause the least disruption to the squirrel's habitat.