A silent and unstoppable massacre is under way in California that could have repercussions across the entire country. From 2010 to the present, it is estimated that more than 66 million trees have died in California's Sierra Nevada forests, 26 million of them in the last eight months alone.

The drought

The factors behind this unprecedented die-off are many; first and foremost, mention must be made of the drought afflicting California — the worst in its history — which is also threatening the survival of giant sequoias (Sequoiadendron giganteum). The snowpack on the Sierra Nevada, California's mountain range, reached its lowest ever recorded level in April 2015.

The bark beetle

Compounding the situation is an invasive insect, the bark beetle. This small beetle, measuring 4 or 5 millimetres in length, attacks the surface layer of wood and is one of the most destructive parasites of conifer forests. The lack of water makes trees more vulnerable to beetle attack.

Fire risk

Extraordinarily high temperatures and a lack of rainfall also risk sparking devastating wildfires, which would further destroy California's forests and endanger the population.

Rust-coloured forests

The ancient and lush forests of the Sierra Nevada, seen from the air, have taken on an unsettling rust colour. According to the US Forest Service, the tree mortality rate has risen dramatically over the past year, increasing by 65 per cent across Tuolumne and Kern counties, an area covering more than 30,000 hectares.

State of emergency

Last October, California's governor, Jerry Brown, declared a state of emergency and established a task force charged with removing dead trees that pose a threat to motorists and mountain communities.

Investing in forests

Tom Vilsack, the United States Secretary of Agriculture, who oversees the Forest Service, has stated that the disaster will be of even greater proportions unless more resources are invested in forest management in California and across the United States in general, urging Congress to take action.

Fighting climate change

Kathryn Phillips, director of the California chapter of the Sierra Club, the oldest and largest environmental organisation in the United States, hopes that the mass tree deaths will convince politicians of the urgency of curbing the pollution that contributes to climate change. "This is a warning for all of us," said Phillips, "we need to reduce emissions and air pollution. We are on the right track but we need to accelerate our efforts."