evidence: Throughout our planet's history, sea level has risen and fallen dramatically. At times, there was no ice at the poles and the ocean was hundreds of feet higher than it is now; at other times, ice covered the planet and sea level was hundreds of feet lower. These changes are part of Earth's natural glacial cycles and have occurred over millions of years. Scientists use sediment and ice cores to learn more about sea level before the advent of tide gauges and satellites. [...] Over the next century, people will be forced to abandon their homes along the coasts as higher tides and increased flooding make life difficult. Many cities, states and countries are already incorporating sea level rise and shifting coastlines into their planning and policy documents. Not only people, but animals will have to move and adapt. Scientists are already working to help Laysan albatrosses establish colonies on higher ground.