It’s well documented that climate change will push species into new ranges, often poleward in latitude or up in elevation. Other human activities, including land use change and introducing new plants and animals to an area, are probably also to blame for the shifts in species, adds Colwell. In the oceans, this change could be happening faster because there’s fewer barriers to swimming creatures. If a fish gets too warm, it’s easier to swim to new, cooler waters than for a terrestrial creature to cross land, with obstacles like mountains, rivers, and roads. This could explain why oceans are changing faster than the land, but ecologists have yet to pin down a definite cause.