The Earth's warming and resulting natural disasters are creating a more dangerous world of desperate leaders and peoples, the Biden administration said in the federal government's starkest assessments yet of security and migration challenges facing the United States as the climate worsens.

The Defense Department for years has called climate change a threat to U.S. national security. But Thursday's reports by the departments of Defense and Homeland Security, National Security Council and Director of National Intelligence provide one of the government's deepest looks yet at the vast rippling effects on the world's stability and resulting heightened threats to U.S. security, as well as its impact on migration.

The 2-month-old California wildfire that threatened the Lake Tahoe resort region over the summer has been declared 100% contained, officials said.

The fire, which scorched more than 346 square miles (896 square kilometers) of the Sierra Nevada and burned hundreds of homes, reached the milestone late Wednesday, according to a report from firefighting officials.

A hefty set of tusks is usually an advantage for elephants, allowing them to dig for water, strip bark for food and joust with other elephants. But during episodes of intense ivory poaching, those big incisors become a liability.

Now researchers have pinpointed how years of civil war and poaching in Mozambique have led to a greater proportion of elephants that will never develop tusks.

Scientists attempting to bring back the near-extinct northern white rhinoceros announced Thursday they would stop harvesting eggs from one of two remaining live specimens involved in an unprecedented breeding program.

French oil and gas major Total deliberately downplayed the threat of global warming from the 1970s onwards, according to research based on interviews with former company executives and internal company documents.

The death toll from days of flooding and landslides in India and Nepal crossed 100 on Wednesday, including several families swept away or crushed in their homes by avalanches of mud and rocks.

Africa's rare glaciers will disappear in the next two decades because of climate change, a new report warned Tuesday amid sweeping forecasts of pain for the continent that contributes least to global warming but will suffer from it most.

The report from the World Meteorological Organization and other agencies, released ahead of the U.N. climate conference in Scotland that starts Oct. 31, is a grim reminder that Africa's 1.3 billion people remain "extremely vulnerable" as the continent warms more, and at a faster rate, than the global average. And yet Africa's 54 countries are responsible for less than 4% of global greenhouse gas emissions.

South Korea set a new goal on Monday for fighting climate change over the next decade, saying it will aim to cut its greenhouse gas emissions to 40% below 2018 levels by 2030.

The country had faced criticism that its initial plan for a 26.3% reduction was too modest. In promising stronger contributions to curb global warming ahead of a U.N. climate summit in Scotland next month, South Korean President Moon Jae-in said the new target represents the "most enthusiastic" objective the country could possibly set under current circumstances.

The humpback chub, a rare fish found only in the Colorado River basin, has been brought back from the brink of extinction after decades of protection, though work must continue to ensure its survival, federal authorities said Monday in reclassifying the species from endangered to threatened status.

The fish, which gets its name from a fleshy bump behind its head, was first listed as endangered in 1967, its habitat severely disrupted by dam construction. Its numbers also declined with the introduction of predatory, non-native aquatic species.

A net zero carbon emissions target by 2050 would be a "great positive" for Australia if it can be achieved through technology and not a carbon price, the prime minister said on Tuesday as he pressures government colleagues to commit to more ambitious action ahead of a climate summit.

Prime Minister Scott Morrison last week agreed to attend next month's climate conference in Glasgow, Scotland, but his government colleagues have yet to approve the commitment he wants to net zero.