Environmental scientists for the most part agree that the human population is growing at an unsustainable rate, to the point that even fertility restrictions and a worldwide pandemic couldn't solve the problem, according to new research.

There are currently more than seven billion people on Earth. And despite the United Nation's (UN) belief that humanity would level off, so to speak, a report published just last month shows that the 21st century may get a lot more crowded than previously thought. The global population will continue to grow to a whopping 11 billion people by the time the year 2100 rolls around.

With this latest study, published in the journal Proceedings of the National Academy of Sciences, the hope of a "quick fix" for environmental problems is shattered, as stringent fertility restrictions or a catastrophic mass mortality would not even bring about large enough change this century to solve issues of global sustainability.

"Global population has risen so fast over the past century that roughly 14 percent of all the human beings that have ever existed are still alive today - that's a sobering statistic," ecologist and professor Corey Bradshaw, from the University of Adelaide, who co-led the study, said in a statement. "This is considered unsustainable for a range of reasons, not least being able to feed everyone as well as the impact on the climate and environment."

Family Matters

In the study, Bradshaw and co-author Professor Barry Brook examined several hypothetical scenarios, such as declining fertility and mass casualties, to see what impact these would have on subsequent population growth rates.

Family planning and birth control, for instance, could be implemented via education programs to try to curb our growing numbers; it worked in China. The country's one-child policy, beginning in 1979, limited families to a single child. The plan - while also leading to a gender imbalance - helped avert 400 million births.

However, "even one-child policies imposed worldwide would still likely result in [5 billion] to 10 billion people by 2100," Bradshaw said in the statement.

In another scenario, the researchers wanted to see what would happen if two billion people died over the course of a five-year period in the mid-21st century, for example, by a war or pandemic. They calculated the world's population would still grow to 8.5 billion by 2100.

"We were surprised that a five-year WWIII scenario mimicking the same proportion of people killed in the First and Second World Wars combined, barely registered a blip on the human population trajectory this century," Brook added.

Although the researchers don't plan on starting a third World War or releasing some catastrophic disease, the results don't deter them from trying fertility reduction efforts, which are obviously more realistic, and ethical. The duo says it could still lead to hundreds of millions fewer people to feed by mid-century, which is better than nothing.

Unfortunately, most of us alive today would not reap the benefits of this type of family planning.

"Our great-great-great-great grandchildren might ultimately benefit from such planning," Brooks said, "but people alive today will not."

Feed the World

Forget about finding room for all these people, these growing numbers will place more stress on Earth's resources, which will struggle to keep up.

Scientists worry about the conversion of forests for agriculture, the rise of urbanization, the impacts on wildlife, pollution, and climate change, according to BBC News. In addition, perhaps most importantly, how can we expect to feed the world as it gets bigger and bigger and consumption rates increase?

When we think about threats to our environment, we picture power plants and deforestation, not our dinner plates. But our need for food, National Geographic reports, poses one of the biggest dangers to our planet.

Our hunger for beef, for example, is already taking a toll on wildlife, habitat and the climate. Nature World News previously reported that by eating less or no meat (that's not to say you have to become a vegetarian), we can simultaneously get healthier and protect the planet.

But if current trends continue and demands for products like meat and dairy increase, the global food supply may not meet future demand. We would have to double the amount of crops we grow by 2050.

"For the first time in human history, food production will be limited on a global scale by the availability of land, water and energy," Fred Davies, senior science advisor for the US Agency for International Development's bureau of food security, said in a press release.

To rise to the challenge, humanity would have to develop more efficient technologies for harvesting crops, according to Davies.

But increasing agricultural practices poses its own problems. National Geographic says that the practice is one of the biggest contributors to global warming, "emitting more greenhouse gases than all our cars, trucks, trains, and airplanes combined." Methane and nitrous oxide are released from cattle and rice farms and fertilized fields, respectively, while the infamous carbon dioxide gas builds up in the atmosphere as forests are cut down to make room for farm land.

More than a third of recent deforestation can be tied to production of beef, soy, palm oil and timber alone.

What Does the Future Hold?

Based on UN estimates, India will boast the most people of any country in the future, with its numbers peaking around 2070 and declining to around 1.5 or 1.6 billion by 2100. But Africa is going to see a population explosion. The population in that region could quadruple, from less than one billion to nearly four billion, the report says, mostly because fertility is falling there much more slowly compared to other countries.

All these numbers and figures may be staggering, but scientists maintain an optimistic outlook.

"These are not predictions," John Wilmoth, head of the UN Population Division, told National Geographic. "These are projections of what will happen if current trends continue. There is still an opportunity to intervene."

"Society's efforts towards sustainability would be directed more productively towards reducing our impact as much as possible through technological and social innovation," Bradshaw concluded.