TWENTYNINE PALMS, Calif. (AP) - At a sprawling desert base, a Marine recharged his radio's batteries simply by walking, while nearby fellow troops examined a rocket artillery system and a drone - both powered by the sun.
Navy and Marine Corps brass, accompanied by green energy executives, showcased the energy-harnessing knee braces and other innovations at a renewable energy demonstration at Twentynine Palms Marine Corps base, one of many such events that have taken place at military bases across the country as part of the Defense Department's unprecedented shift away from fossil fuels under the Obama administration. The Pentagon has invested millions over the past decade into everything from hybrid electric ships to wind turbines.
While a growing number of military leaders have declared global warming a national security threat, the strategy clashes with President-elect Donald Trump's vow to end policies that "undermine" fossil fuel producers. Trump has a chosen a Cabinet with climate change skeptics, though his pick for defense secretary, retired Marine Gen. James Mattis, has advocated green technology to curtail risky fuel-supply runs for troops in conflict zones.
It's not known if Mattis would support buying alternative fuels for ships and aircraft, among the military's biggest petroleum users. He didn't respond to requests seeking comment.
Republican lawmakers have lashed out at many of the green initiatives for the Defense Department - one of the world's largest energy consumers - especially the Navy's Great Green Fleet that deployed ships run partly on biofuel amid falling oil prices.
Military leaders said alternative energy makes warriors more agile and effective on today's battlefields.
At the recent demonstrations, a Marine wore knee braces with tiny generators that transformed the energy he produced from walking to recharge batteries. The technology allows troops to generate their own power for as long as three days. The event also featured a M777 howitzer and a drone that use solar power.
"To do something other than continue these programs would be a mistake," said Joe Bryan, the Navy's deputy assistant secretary for energy. "My expectation is that will be recognized no matter where people are on the political spectrum."
Rising sea levels threaten Navy bases worldwide, and it would be "shortsighted" for the military not to address climate change, Bryan said.
Trump's transition team did not respond to questions about whether it would end the strategy.
Republican lawmakers have said the Pentagon has propped up the alternative energy industry, investing in programs that are not sustainable. The Defense Department has been working toward generating 25 percent of its power from renewable sources by 2025. The Navy and Marine Corps set a goal to draw half of its power from renewable energy sources by 2020.
GOP legislators have criticized the Obama administration for spending roughly $120 billion on climate change initiatives while putting in motion $1 trillion in defense cuts.
"I hope the new administration allows the U.S. military to focus on the most important defense issues like fighting ISIS, defending from Iranian and North Korean belligerence, and guarding against aggression from China and Russia," Colorado Republican Rep. Ken Buck said in a statement to the Associated Press. "Our military should use the most cost-efficient fuel sources, rather than burning money on green energy experiments."
The most contentious initiative has been the purchase of biofuel for ships. Critics said while ships may leave port with a biofuel mix, they still must rely on foreign oil in many places near battlefields and the plant-based fuel has become more expensive than traditional fuel.
According to a 2015 report from the Government Accountability Office, Congress' research arm, the Pentagon paid $58.6 million for 2 million gallons of alternative fuel from 2007 to 2014, or about $29 per gallon. At the same time, it spent $107.2 billion for 32 billion gallons of petroleum, paying about $3 per gallon.