No better introduction to the current global environmental crises is available than the United Nations' huge, important, free-to-download document, the GEO-6 Environmental Outlook of 2019. Here's some of what it says:

New information:

Links for Learning about The
EARTH'S ENDANGERED BIOSPHERE
Shortcuts to topics:
ENDANGERED SPECIES | GLOBAL WARMING/CLIMATE CHANGE | HUMAN OVERPOPULATION | NUCLEAR WASTE POLLUTION | SIMPLE LIVING | WATER ISSUES | VEGETARIANISM | MISCELLANEOUS ISSUES | ENVIRONMENTAL ORGANIZATIONS

Endangered Species:

Global Warming/Climate Change:

Human Overpopulation:

Miscellaneous Issues:

Nuclear Power & Waste:

Pollution:

Simple Living/ Voluntary Simplicity:

Vegetarianism:

Water Issues:

Once you're oriented, get involved!