PHOENIX (AP) - On American Indian reservations throughout Arizona and the rest of the country, tribal officials say global warming is already changing lives and solutions are needed quickly.

Representatives from more than 50 tribes throughout the United States gathered Tuesday near Yuma for a two-day Tribal Lands Climate Conference.

From Alaska to Arizona, each tribe represented said it was experiencing changes in precipitation, temperature and wildlife that appear to be brought on by climate change. These alterations are threatening their people's land, health and culture.

Greenhouse gases released into the atmosphere trap the sun's energy on Earth's surface, causing the planet to warm. Government models project temperatures to rise as much as 5 to 10 degrees in the 21st century. Even a warming of only a few degrees adds a tremendous amount of energy to Earth's system.

Weather events like hurricanes will likely grow in intensity, said Dr. Robert Corell, chair of the Arctic Climate Impact Assessment. In the Southwest, more drought is a near certainty.

"We basically have two seasons now _ hot and dry and cold and dry," said Robert Gomez, director of the environmental office of the Taos Pueblo reservation in New Mexico.

For tribal communities whose culture and sustenance are dependent on the natural environment, climate change poses an immediate threat.

In the Lower Colorado region, the past seven years have been the driest in a century, U.S. Bureau of Reclamation officials said.

Shorter winters and earlier springs and summers are affecting planting schedules and harvests around the country. Seasonal changes are also affecting animals' migration and hibernation.

As temperatures warm, plant and animal species crucial to tribes' religions, diets and culture migrate north in search of colder weather but reservation boundaries are fixed.

"As our species migrate off, we don't have the legal right to follow them," said Terry Williams, fisheries and natural resources commissioner for the Tulalip Tribes.

If nothing is done, "within the next 20 to 25 years, our culture will be terminated, because the necessary species will be gone," Williams added.

Many tribes are working to combat the effects of climate change. Some are researching ancient customs to find how their ancestors built energy-efficient homes and cultivated erosion-resistant plants.

Others are exploring modern alternative-energy projects that offer energy independence and economic opportunity.

"We're all singing the same song," said Colin Soto, spokesman for the tribal elders of Arizona's Cocopah Tribe near Yuma. "We're trying to tell the rest of the world, 'Look, we're seeing these things, and you're not doing anything about it.' If the animals die, we die. If the river dies, we're gone."