Since it began in 1945, the United Nations (UN) has played a big role in tackling environmental issues. They've done this through many programs and agreements. Here are some key things they've achieved:

• In 1972, they started the UN Environment Programme (UNEP).
• They have agreed on more than 500 environmental agreements with different countries.
• In 2015, they created the Paris Agreement. This goal is to keep global warming to less than $2^\circ$C.
• There’s a plan called the Global Biodiversity Strategy that aims to protect 30% of the Earth’s surface by 2030.

Overall, the UN has been very important in bringing countries together to work on keeping our environment safe and sustainable.