Biodiversity is a contraction of the phrase "biological diversity," and refers to the variability of life within a species (judged by the variations in its genetic makeup), an ecosystem, a region and even across the planet. The biodiversity of the Amazon, one of the most biodiverse places on Earth, would include the terrestrial species found in the rainforest, the birds that fly in its skies and the aquatic creatures that swim in the Amazon River. But one could also examine the biodiversity of the Amazon River itself. Biodiversity varies widely across the globe, from places of high biodiversity, such as rainforests and coral reefs, and areas of lower biodiversity, such as agricultural fields. High biodiversity is often considered a sign of a healthy ecosystem, and many conservation efforts are aimed preserving biodiversity. Read below for stories on studies of biodiversity.