A group of scientists is hurrying to document ancient ruins on the U.S. territory of Puerto Rico.The sites, along Puerto Rico's coast, date back a few thousand years.The scientists are working as fast as they canbefore rising sea levels destroy a large part of the island's history.Scientists hope to use the three-dimensional (3D) images they have takento help identify which sites are most at-risk to natural disasters and other dangers.Falko Kuester is director of the Cultural Heritage Engineering Initiativeat the University of California, San Diego.He said, "A big part of what we're working on is to make the invisible visibleand make sure it stays in our memory."The university, known as UCSD, is involved in the research project.Also involved are its Scripps Institution of Oceanography and Para la Naturaleza,an environmental group based in Puerto Rico.The work started in August 2017.Scientists first explored a large stretch of land along Puerto Rico's north coast.That area includes a ceremonial center used by the Taino Indiansabout 2,000 years ago, said Isabel Rivera Collazo.Rivera is an environmental archaeologist at UCSD and directing the project.She said the scientists found what appears to be a large settlement just east of the ceremonial site.It was discovered with help from drone aircraft and other technology, including 3D images.She added that scientists were also able to map out the shape of the ceremonial site.The Tainos once lived on many islands in the Caribbean Sea.But after the arrival of Christopher Columbus and other Europeans,the indigenous people were nearly all killed.Rivera said, "Up to today, there is still a lot we don't know about indigenous culture along our coasts.It's not in our history books...we want to recover that information before it disappears."Puerto Rico's Department of Natural Resources has said the sea level around the islandis rising by more than 3 millimeters every year.However, climate change has more immediate effects.These include the destruction of the island's coastline and natural habitats.Some scientists say that warmer temperatures in the Caribbean increase the number and strength of storms.Puerto Rico faces the possibility of storms every year for six months during the Atlantic hurricane season.Scientists noted that large amounts of water caused by Hurricane Mariawashed away part of the area they are studying.Eric Lo is an engineer with UCSD's cultural heritage initiative.He flew to Puerto Rico in August 2017 to launch the project one month before Maria struck the island.Lo was surprised at what he saw when he returned to the U.S. territory months later.He said, "Pieces of land where I had stood and flown the drone didn't exist anymore. They were underwater."Scientists are now trying to find out how badly the hurricane and loss of landhave affected the archaeological site they are studying.The scientists are using 3-D models based on drone images to measure areas and explore other details.