The waters along the west coast of North America are some of the most biologically productive in the world. Cool water from high latitudes flows southward from the edge of British Columbia to Baja; this is the California Current. At the same time, prevailing northeasterly breezes blow from land to sea and push ocean surface waters away from the coast. As a result, cooler, nutrient-rich water rises up from the depths to take its place—a process known as upwelling. The combination of cool water and abundant nutrients promotes the growth of plant life in the sea, from microscopic phytoplankton to dense kelp forests. Those plants—primary producers—become the center of a food web that includes highly productive fisheries, sizable populations of marine mammals (whales, seals, dolphins), and vast numbers of sea birds. This productive ecosystem can extend as much as 500 kilometers (300 miles) out from the coast.