Inability to accept change

Us. Us blowing it to smithereens. Us plundering it to extinction. Us poisoning it to extinction. Us overrunning it to extinction. Take your pick.

Terrorism

We are our own worst threat.

Short term: us

Long term: big fucking asteroids

Long, long term: the sun

Squirrels lil fuckers. They have no regard for human life.😄

a nuclear war

communism

Climate change. If the temperature rises by just a single degree the entire coastline in the US will drop to below sea level. Lots of agriculturally dependant countries are already experiencing unprecedented floods and droughts.

The immense power of evil people.

In terms of sterilising earth it might be a cosmic intruder in form of an asteroid, in terms of "life" meaning many animals plus us humans: human shortcomings, human idiocy.

Human industry.

Deez nuts