Time travel is hard, which makes learning about the earth’s past climate difficult. For example, what happened to the earth’s temperature at the end of the Cretaceous, when dinosaurs went extinct? To find out, we have to use proxies – ancient objects whose form or composition indicate the climate at the time they were made.…

This week I am working in the paleobotany collections at the Denver Museum of Nature and Science. A good place to work becomes an even better one if one’s visit aligns with the transit of Venus across the sun. I spent the evening at the museum, watching the one immense object hurtle past another even…

The foresummer has arrived, bringing hot and dry conditions to the desert. Despite the adverse conditions, many species are moving through the reproductive stage of their life cycles. Saguaro cacti are in full bloom – the flowers are especially beautiful at dawn and dusk. This year’s weather has been very favorable, with dozens of flowers…

Around the world, what determines the height plants grow to? Some places have trees a hundred meters high, while others are limited to annual plants shorter than a few centimeters. This range of variation is striking, but also important – canopy height helps us predict competition between species, ecosystem carbon and water fluxes, biomass accumulation,…