Why don't pine trees lose their needles in the winter?

In the winter, most of us are used to seeing bare tree branches  – but some trees, like firs, pines, and spruces, don’t usually lose their needles when it gets cold. We asked forest ecologist Diana Macias to help us understand why.   Got a Moment of Um question for us? Go to BrainsOn.org/contact to send it to us, and we’ll root around for the answer. See omnystudio.com/listener for privacy information.