The earth slows down stops then starts spinning again. Gravity would become weaker and weaker one side of the earth would be perpetual night and the other side perpetual day the atmosphere would dissipate into space along with anything loose on the surface which includes all the water we have all life would perish. Slowly, as the earth starts to spin again gravity might pull some of its materials back down but hardly enough to make a difference. The earth would be a barren wasteland.

Why would gravity become weaker and things float off into space? Gravity has nothing to do with the earth spinning. It’s a property of mass. The mass of the earth wouldn’t change because it stops spinning.

Tides would stop. One side would heat up, the other side would cool down. The diurnal cycle of animals and plants would cause havoc, but the planet itself wouldn’t have a huge issue. Everything on it, yes, but that’s because the ecosystem is built around the flow around the planet, not because of the physical motion.

The planet has been slowly slowing down for millennia and will eventually stop.