Quiz time – in the map below, can you name the two species whose distributions are shown in red and blue dots? You can see that the occurrences of A are associated with warmer temperatures, whereas the occurrences of B are associated with colder temperatures and higher latitudes. Whatever you guessed, you were probably wrong.…

The surest sign of winter in my Arizona mountains is the fall change of colors. The summer’s greens are replaced by greys and browns, as ferns die back, sunflowers set seed, and the trees lose their last leaves. The change is remarkably synchronous. It feels like in a single day, summer is replaced by winter.…

Quaking aspen is my favorite tree. In the autumn its leaves change color to a warm yellow, making a perfect contrast against its white and black bark. At sunset the forest glows with the light filtering through the stands of this species. I never stop learning new things about it, either. On a recent hike…

Last week the remnants of Hurricane Simon passed through Tucson. The city received just an inch of rain, but the story was different up in the mountains. The summit of Mt. Lemmon, rising almost 7000′ above the city, recorded five inches of precipitation in a single day. The reason is orographic lift – mountains force…