The Iditarod and similar races have increasing challenges to their survival in the 21st century, for what reason?

Answer 1

Erratically warmer temperatures, disappearing ice and snow, fiercer storms, new growth of vegetation
The phenomena are due to accelerating climate change. The Iditarod is a race for people, dogs and sleds, run annually over approximately 1,000 miles (1,600 km) in west and central Alaska. Studies by the U.S. National Oceanic and Atmospheric Administration (NOAA) found that in the 21st century the region is warming at a rate twice as fast as the global average, with the race’s starting line in Anchorage recording the second-highest winter temperatures in Alaska’s history. In winter 2019 alone, monthly temperatures were about 7.2 degrees Fahrenheit higher than normal and the north Bering Sea as much as 28.8 degrees Fahrenheit.