Britannica Presents Earth’s To-Do List for the 21st Century

Learn about the major environmental problems facing our planet and what can be done about them.

Since the end of the last ice age, humans have developed tools and machines and have modified the land for agriculture and long-term settlement. As the population has grown and new technologies have spread across cultures and continents, more and more of the planet’s resources have been pressed into serving the species. In the process, human activities have disrupted the natural order of the environment by depopulating and eliminating species and adding harmful chemicals to the air, water, and soil—activities that are changing the climate and the structure and function of ecosystems, as well as the biological communities they contain. Solving the critical environmental problems of global warming, water scarcity, pollution, and biodiversity loss are perhaps the greatest challenges of the 21st century.

Will we rise to meet them?

First Earth DaY – 1970

20 million

Americans demonstrated for a healthy, sustainable environment in massive coast-to-coast rallies

Earth Day 2000


Environmental groups in a record 184 countries reached out to hundreds of millions of people

Know the Causes

Human action has triggered a vast cascade of environmental problems that now threaten the continued ability of both natural and human systems to flourish. While it is difficult to distill the major drivers of these problems into a brief list, the following articles provide insight into some of the overarching causes behind many of our most pressing crises. Read about the Industrial Revolution, population growth, consumerism, and other big forces that have led to an Earth that needs saving.

Know the Solutions

While it is easy to become discouraged by the current and projected impacts that these environmental problems have upon Earth’s biosphere, a number of solutions have emerged. Most involve changing the way we view the planet and its resources and leveraging regulatory and policy tools to establish sets of rules that incentivize the sustainable use of Earth’s resources.


Which gases play an important role in climate change? What percentage of scientists agree that humans contribute to this process? Test your knowledge of this “hot” topic with this quiz.


There are a lot of ecosystems in the world. How much do you know about the different types of ecosystems?iption


Do you know about the threats facing nonhuman life on Earth? Take this quiz to test your knowledge.