If you have seen the 2013 film Gravity, the accident caused the astronauts to break off from the ship was due to debris in space. If satellites are not disposed of properly, the parts could become high-speed bullets leading to a chain reaction destroying everything on its way, or the Kessler Syndrome.
The Outer Space Treaty signed in 1967 address this issue. All countries involved in outer space project signed up to work with each other to avoid the situation. However, there are still over 750,000 fragments that are over the size of 0.4 inches flying in the orbits. This could lead to serious consequences including massive communication blackout on earth.
The Europe Space Agency looks to clean up the debris from the satellite orbits, but the key always is to stops polluting the space.
To capture a retired satellite, the scientist developed an arm that could sync up the motion with the satellite and retrieve the entire structure back in the atmosphere.
For unstable satellites, the ESA is trying to use a net and capture it.
Over the years, there have been efforts to clean up space.
A project led by Japan, KITE, fell short when the spacecraft tether failed to deploy.
In 2018, a British Satelittle, the RemoveDEBRIS, has become the first ever to function in the orbit, using a net the capture large debris.