If I had all the resources in the world I would try to stop overpopulation problems since that is the root of all the environmental issues in the world. 

As more and more people inhabit the earth, people use more oxygen and emit more carbon dioxide so there needs to be more trees. Unfortunately, more people also take up more room which forces deforestation thus leaving us with less oxygen. Similarly, overpopulation causes the destruction of natural habitats and taking animals' homes, thus leading to extinction of animals' and beautiful natural views getting quickly urbanized and turned into factories or malls. Furthermore, as there is more carbon dioxide it tends to be one of the biggest heat trapping gas that triggers the greenhouse effect which leads to global warming as a whole. 

Although this problem may not seem that dire in that it's hard to realize how fast the population is growing, logically it makes sense. Going back many generations to someone's great grandma which hypothetically had your grandma and her two siblings and then your grandma has your mom and her sibling and your grandma's siblings each have 3 children making 8 cousins of your mom that all will go on to have 2 children and so on adding 16 new generation people only coming from your great grandma and grandpa. Moreover, studies such as ourworldindata.org have shown that there is growth of 83 million people annually or 1.1% per year. This is a significant number of people and if it stays at that rate people will not only not have a place to live but also the earth will start to rapidly deteriorate trying to hold all these people. To put it further into perspective, the population went from 1 billion in 1800 to 7.9 billion in 2020 to 8.1 Billion currently. So, this is a big problem that should be addressed rapidly. 

In order to attack overpopulation and its problems, simply bringing awareness is important. The more people know about these issues, the more people will seek to address it themselves whether that be having less kids or thinking about adopting. People can also try to attack the problems that are caused by overpopulation like extinction, deforestation, or the greenhouse gas effect by lowering their carbon emissions and looking to more sustainable energy sources, packaged and eating.