In the most ambitious U.S. effort to stave off the worst of climate change, President Joe Biden signed executive orders Wednesday to transform the nation's heavily fossil-fuel powered economy into a clean-burning one, pausing oil and gas leasing on federal land and targeting subsidies for those industries. The directives aim to conserve 30 percent of the country's ocean waters in the next 10 years, double the nation's offshore wind energy, and move to an all-electric federal vehicle fleet, among other changes. Biden's sweeping plan is aimed at staving off the worst of global warming caused by burning fossil fuels. But his effort also carries political risk for the president and Democrats as oil- and coal-producing states face job losses from moves to sharply increase U.S. reliance on clean energy such as wind and solar power. Biden has set a goal of eliminating pollution from fossil fuel in the power sector by 2035 and from the U.S. economy overall by 2050, speeding what is already a market-driven growth of solar and wind energy and lessening the country's dependence on oil and gas. The aggressive plan is aimed at slowing human-caused global warming that is magnifying extreme weather events such as deadly wildfires in the West and drenching rains and hurricanes in the East. Biden acknowledged the political risk, repeatedly stating that his approach would create jobs in the renewable energy and automotive sectors to offset any losses in oil, coal or natural gas. President Donald Trump, who ridiculed the science of climate change, withdrew the U.S. from the Paris global climate accord, opened more public lands to coal, gas and oil production and weakened regulation on fossil fuel emissions. Experts say these emissions are heating the Earth's climate dangerously and worsening floods, droughts and other natural disasters. Biden also is elevating the warming climate to a national security priority, directing intelligence agencies, the military and others to do more to prepare for the heightened risks. The conservation plan would set aside millions of acres for recreation, wildlife and climate efforts by 2030 as part of Biden's campaign pledge for a $2 trillion program to slow global warming. Biden also will direct all U.S. agencies to use science and evidence-based decision-making in federal rule-making and announce a U.S.-hosted climate leaders summit on Earth Day, April 22.