cgundersen wrote:In thinking about how relatively unchanging the Sierra have been over the years, it reminded me that there have been some changes since I took my introductory hike on the High Sierra trail in the early '70s... I've started to run across more dried up lakes/tarns.
I'm sure others have noted substantive changes. What next? cg
Interesting topic – Too complex to have but one answer. The physical changes mentioned: drying/filling in of lakes and such, seem to fall under the Sierra’s natural evolution process. (FYI, Yosemite’s Mirror Lake really was once a lake)…chit that is supposed to happen over time. These changes are inevitable. While other changes mentioned – the frogs – Obviously much discussion available as to why - many causes oft repeated: parasites, viruses, trout competition.
The Eagles vs. Ravens comment is compelling. This summer, at a Tuolumne campfire, a Ranger expert in residence explained that the raven’s primary diet is trash and road kill; seems they do not hunt live food. She also cited her own multi-year study saying that Ravens in Tuolumne do not winter there and interestingly, none are ever found at altitude until after the road opens for the season. She stated that this year, only one day after the opening date, multiple pairs were first observed, (same last year too) in the Meadows, obviously suggesting a link between cars and available food supply...Smart birds. She went on to suggest there is indeed competition with the eagles for food, but dismissed this as a major cause for not seeing the numbers of eagles today as in years past…seemingly to suggest that the eagles are still abundant. She reasoned that although Raven numbers are up, Eagle numbers remain high too, but have moved /prefer wilderness. The reason we see more Ravens is that they advantageously co-mingle among people (read trash) while Eagles prefer the less traffic areas - thus things may have changed a bit here.
In my travels this year was glad to observe a rebirth of the ground squirrels…Suggest the main cause of the recent Sierra scarcity of these small critters (Squirrels, chipmunk types, Pikas, etc) has to do with yearly water supply availability. For the past 5+ seasons the Sierra experienced somewhat of a drought; water was not available and thus little vegetation - nothing thrived. No grasses – no seeds – no critters. Perhaps biologically these foragers sense more water = more food = bigger litters. Where in recent years past there was a noticeable shortage of these campsite pests (BTW, Steller’s Jays too), this season, with all the water, all appears abundant again, as if they were in some sort of extended hibernation.