They sent thousands of firefighters, 25 helicopters and an arsenal of more than 400 fire engines and 70 water trucks. Yet the fire still advanced…. The blazes in Sierra forests have exposed the domino effects of climate change on firefighting challenges: Frequent heat waves and overall higher temperatures have desiccated West Coast flora, making it more vulnerable to large fires. Droughts have weakened trees, encouraging insect infestations that have contributed to the deaths of close to 150 million trees. This creates more fuel for fires.