Orca numbers in Puget Sound are rebounding a bit, but the whales are still in danger, as today’s Seattle Post Intelligencer reports.

Looking at the oscillations in the PI’s chart (which doesn’t reproduce well when copied, so you’ll have to look at it here) is also a reminder that there’s a tremendous amount of variation in nature. That makes it hard to select indicators of ecosystem health that are very reliable gauges. Orca (and salmon) numbers, for example, change a lot even in undisturbed ecosystems. Discerning the hand of human impacts from the natural variability is hard.