The Challenge of Our Age: Managing Climate, Population, and Migration

The current climate and environmental crises mean we must plan for a net zero world that provides healthy and safe lives with low environmental impact for 10 billion people by 2050. At the same time, the world’s economy will double or possibly even triple. Managing these situations simultaneously is the challenge of our age.

Climate change is increasingly recognized as a threat to global, regional, and national security. At the same time, the global energy transition—which is critical to curbing climate change’s harshest impacts—is disrupting business in countries worldwide. Against this backdrop, the global population continues to increase. Currently at 8.2 billion, the UN predicts a peak of 10.3 billion people by the mid-2080s. Much of that growth will occur in Sub-Saharan Africa where 600 million people still lack access to electricity, water, and sanitation. So, what does a climate-resilient world of 10.3 billion look like? And how do we ensure everyone has healthy, fulfilling, sustainable, and secure lives?

Threats and Opportunities

One of the biggest concerns is food security. One-third of the global food supply is produced by smallholder farms, which operate five out of six farms globally. Agriculture also provides jobs for around 30% of the world’s population, making it the single largest employer worldwide. But increasing temperatures and humidity has significantly increased the number of days each year that it is physiologically impossible to work outside, which if persistent, threatens food production. Climate impacts—like those from rain-fed agriculture and changing precipitation patterns— are already incurring a heavy economic cost on countries around the world, many of which are simultaneously dealing with weak economies and lack the institutions and resources to adequately respond. As the pressures of climate change intersect with existing vulnerabilities, we are likely to see increased numbers of climate-related migrants crossing borders. One study estimates that over the next 50 years, a 4˚C warming would make parts of the planet uninhabitable, disrupting the lives of nearly 3 billion people.

We produce enough food to feed 11 billion people and yet 7 million children die each year of hunger and preventable diseases.

In 2015, global leaders meeting in Paris agreed to limit climate change to just 2˚C warming by 2100, with an aspirational target of 1.5˚C. To meet this goal, science suggests we need to cut global carbon emissions by half by 2030 and hit net zero by 2050—which is extremely challenging. Still, we have the technology, resources, money, scientists, business leaders, and innovators to do it. What we lack are the politicians—or the political will—and policies to make the rapid transition to a just and fair net zero emission economy. What’s clear is that the environmental and climate crisis is not caused by too many people, but because humans consume resources in a deeply inefficient way while using 19th-century technology to power societies. 

State of the Environment

For the first time in our planet's 4.5-billion-year history, a single species—humans—are dictating its future. Eight billion people are having as much effect on the Earth’s environment as a giant meteorite, mega-volcanoes, or the movement of the continental plates. Humanity is a new geological superpower that has driven Earth into a new geological period called the Anthropocene.

While higher income countries are home to about half of all migrants, they host just 14% of global refugees.

We move more soil, rock, and sediment each year than all the other natural processes combined. There are 1.3 billion motor vehicles, 2 billion personal computers, and more mobile phones than people on Earth. Plastics litter our rivers and oceans and microplastics have been found in human blood and breast milk. We have cut down more than half the trees on Earth (3 trillion) since the beginning of civilization and have documented 800 human induced extinctions—including mammals, birds, reptiles, amphibians, fish, invertebrates and plants.

State of Humanity

Earth’s 8 billion people are not all equally liable for environment degradation and greenhouse gas emissions. For example, the richest 10% of the world’s population emits 50% of carbon pollution from lifestyle emissions into the atmosphere. The richest 50% of the world’s population emit 90% of carbon pollution into the atmosphere. The poorest 4 billion people have contributed only 10% of the carbon pollution in our atmosphere.

Currently, around 700 million people live on less than $2.15 a day, while another 4.5 billion people live on less than $10 a day. Poor people in developing countries can spend up to 80% of their income on food, compared to less than 10% for Americans. We produce enough food to feed 11 billion people and yet 7 million children die each year of hunger and preventable diseases. 825 million people go to bed hungry every night without access to adequate food. This as Americans waste about 141 trillion calories worth of food every day. That adds up to approximately $165 billion per year: four times the amount of food Africa imports each year. Water sanitation is also an issue: Approximately 2.2 billion people do not have access to safe drinking water, 4.2 billion lack access to water sanitation services, 3 billion do not have access to basic handwashing facilities, and nearly a billion people live without electricity.

Population and Migration

The global population has more than doubled since 1970. The main reason for this massive increase is the demographic transition. In the earlier stages of a country’s development, societies tend to have high child mortality rates that are offset by high fertility rates, leaving the population relatively stable. Couples have as many children as they can to ensure that on average two survive to adulthood. As societies develop a more stable food supply, improve sanitation, and make treatment for common diseases widely available, mortality rates drop rapidly. But in many cases, fertility rates stay high for a while. The number of babies born stays the same, but as nearly all of them make it to adulthood, the population expands rapidly. Depending on how large the time lag is between the falls in mortality and fertility, the post-transition population can be between 4 and 10 times higher than pre-transition, and in rare cases, even more.

As well as reducing $7 trillion in taxpayer’s subsidies, there are huge financial gains from switching to renewable energy, which is cheaper and more flexible than fossil fuel energy.

Many people assume that universal access to family planning and contraception are key to reducing fertility rates quickly. While important, the first demographic transition can be traced to the European Enlightenment, just before the 19th century, when these services were not available. Instead, it is women’s education (up to and beyond the secondary school level) that is critical to women’s empowerment and reducing fertility rates. The rapid spread of vaccinations and the expanded food supply created by the green agricultural revolution in the 1960s meant that at its peak, global population was growing at more than 2% per year. In 1950, each woman gave birth on average to five live babies. Now that the demographic transition has happened in many countries, the figure is below 2.5. However, while the average birth rate is falling every year, the world’s population is still growing by 200,000 a day. The United Nations predicts that the population will rise to 10 billion people by 2050 and stabilize by 2100—with another 2 billion people to support by the end of the century. Some argue that these new populations will eventually emit more and more greenhouse gasses as societies continue to develop. But the climate crisis is happening now, and the world needs to be carbon neutral by 2050. This  means by the time poorer nations have developed enough to have a large middle-class, we will need to  develop a fully functioning global green sustainable economy. Otherwise, it will be too late.

The global energy transition will not succeed if it is not paired with robust support for rapid sustainable development in developing countries.

In 2023, 184 million people (about 2.3% of the world’s population) lived outside of their country of nationality, including 37 million refugees. Migration is caused by complicated social, economic, and geopolitical factors. There are push factors when economic, social, environmental, and political hardships force people to move. And then there are pull factors with better jobs, pay, education, and prospects in other regions or countries that encourage people to move. Migration can have both positive (a young workforce, brain gain, and building economic resilience) and negative (strain on resources, intellectual brain-drain, reactionary politics) impacts on countries. While higher income countries are home to about half of all migrants, they host just 14% of global refugees.

These migration numbers do not include internally displaced people, forced from their homes who remain within the borders of their country. Extreme weather events, for example, have historically been more likely to result in short-term, internal displacement than cross-border migration. In 2023, the number of internally displaced people worldwide was 71.1 million. While Russia’s invasion of Ukraine forcibly displaced 16.8 Ukrainians that year, 53% of internal displacements were triggered by weather-related or geophysical disasters. The catastrophic climate-intensified flooding in Pakistan triggered 25% of global disaster displacements and severe droughts over the Horn of Africa displaced 3.3 million people, propelling climate-related hazards into the public sphere, with many headlines referring to those displaced as “climate migrants” or “climate refugees.” With the ever-increasing number of extreme weather events and changing precipitation patterns, the numbers of people displaced by disasters will rise.

10 Billion Can Be Green

The global shift away from fossil fuels to renewable energy needs to accelerate at least five times faster. Critical to this is the removal of fossil fuel subsidies which, in 2022, were estimated to be more than $7 trillion—about 7% of the World’s GDP. As well as reducing $7 trillion in taxpayer’s subsidies, there are huge financial gains from switching to renewable energy, which is cheaper and more flexible than fossil fuel energy.

The global energy transition will not succeed if it is not paired with robust support for rapid sustainable development in developing countries. For example, providing energy access to the 600 million Africans who currently lack electricity must be prioritized alongside the global shift to renewable energy if we are to meet our global climate goals. Sending girls to school, supporting smallholder farmers with the resources to invest in climate-resilient agriculture, and investing in economies that can support jobs for burgeoning youth populations are keys to a future that is climate-proof and secure. Lifting people out of extreme poverty reduces their vulnerability and creates more secure and stable societies. Ultimately, there is no reason why 10 billion people cannot live healthy, fulfilling, sustainable, and secure lives—if we get the economics and politics right. 

Mark Maslin is a professor of Earth System Science at the University College London. Shooka Bidarian is an environment correspondent and Climate Reality Project leader in the UK.

Cover photo: A farmer examines the parched soil in his corn field. Shutterstock/Edgar G Biehle.