Why are we doing this ?

Well this is a great question that I hope most have been able to answer with the info on this site.

As the world has become the modern place we live the materials we use for a variety of tasks has changed and indeed new tasks and materials have also developed. Much of this material is one form or another of plastic which is derived from petroleum (oil), consequently they take considerable time for the breakdown of all the material back to "nothing".

While they break down the materials break into smaller pieces, which wildlife mistake for food, which has no nutritional value, but perversely act as a poison that takes various time frames to cut life short. The end result is death via starvation, drowning, contamination and lack of reproductive ability to name but a few results. Or like this bird, marine mammals, fish get trapped in the old ghost nets and six pack holders.
20% of marine debris originates on land, which means that it has drifted far afield landing on our shores, making an eyesore, but more importantly contaminating our ecostystem, with a variety of toxic chemical compounds as it breaks down, which may take hundreds of years. So it follows the trash we leave on the beach that disappears is likely causing the same problems on a shoreline over the horizon, disturbing some one else.

This is one example of many of what is referred to as trans boundry pollution. The same principles apply to materials in their gaseous and liquid forms.

As you begin to think the seemingly innocent plastic wrapper thrown on the ground that is picked up by the wind and blown to a variety of places until it gets stuck some where, could be in a tree or the throat of an endangered Hawksbill turtle. If of course not got by a net, poacher or run over by a boat.
So in short we are doing this in order to assist reduce the impact on the life forms that provide a vital part of the ecosystem, that provide us with fresh air and food to sustain our healthy life.