Global population has already reached too high a level, and increasing demand for resources is outstripping the Earth’s ability to sustainably support it at current levels of consumption, a new study warns.
A team led by Corey Bradshaw found that humanity is living far beyond the limits that our planet can sustain in the long term. The research is based on demographic data collected over two decades, according to Science Alert.
Ecologists describe the ability of an environment to support a species’ population as a right “carrying capacity”. It is an estimate of how many individuals of a species can survive in the long term, given the resources available and the rate at which they are replenished.
Our species, Homo sapiens, is particularly adept at pushing these limits, tending to find technological solutions to overcome the natural restrictions on resource regeneration – particularly through the exploitation of fossil fuels.
The shift to fossil fuels in transportation and other industries fundamentally enabled rapid population growth in the 20th century—something that becomes evident again in the context of global tensions affecting energy supplies. The current population of the Earth is about 8.3 billion people.
“Current economies, based on continuous growth, seem not to recognize the limits of regeneration that constrain population expansion, as fossil fuels artificially compensate for this difference”the research team says.
“The Earth Can’t Keep Up With How We Use Resources”
Bradshaw and colleagues produced an evidence-based estimate of humanity’s carrying capacity, using ecological growth models to track changes in population size and growth rates over the past two centuries, both globally and regionally.
Researchers distinguish between maximum carrying capacity—the absolute theoretical limit, regardless of famine, disease, or war—and optimal carrying capacity, where population size is sustainable and provides a minimum standard of living.
“Earth can’t keep up with how we’re using resources. It can’t even support current demand without major changes. Our results show we’re pushing the planet beyond what it can handle.”says Bradshaw.
According to the study, until the 1950s the human population was growing at an increasingly rapid rate, but in the early 1960s this rate began to slow, even as the total number of people continued to grow.
“This change marks the beginning of what we call a negative demographic phase”Bradshaw explains. “It means that adding new people no longer leads to faster growth. Our analysis shows that global population could peak between 11.7 and 12.4 billion people in the late 2060s or 2070s if current trends continue.”
The maximum capacity has been exceeded
About 12 billion is the estimated maximum capacity, but it is far from the optimal level under current consumption conditions. Researchers estimate that the optimal level would be around 2.5 billion people.
This is the first study to examine the relationship between the rate of change in per capita population and long-term average population size.
The results show that human societies have moved from a model in which more people meant faster growth to one in which that growth begins to cap: as the population grows, the rate of growth declines.
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Even under these conditions, the current population already exceeds the sustainable capacity estimated by researchers. The gap between the optimal level of 2.5 billion and the current population of 8.3 billion may explain the overconsumption problems facing humanity.
For example, in January this year, the United Nations announced that the world was in a state of “water bankruptcy”. Animal populations are in decline because they cannot compete with humans for resources and cannot keep up with our level of consumption.
The situation is not hopeless
Relying on fossil fuels to increase the Earth’s short-term carrying capacity – for example, to produce fertilizers or to sustain our lifestyles – does not offer a viable solution. At the same time, these fuels contribute to human-induced climate change, which affects ecosystems and natural resources globally.
The study also shows that variations in global temperature, ecological footprint and total emissions are better explained by population growth than by individual consumption growth.
“The systems that support life on the planet are already under pressure, and without rapid changes in the way we use energy, land and food, billions of people will face increasing instability”warns Bradshaw. “Our results show that these limits are not theoretical, but already manifest.”
However, researchers say the situation is not hopeless: “The Earth cannot support future populations – or current ones – without a major shift in the way we use land, water, energy, biodiversity and other resources”the study shows.
“Smaller populations with lower levels of consumption deliver better outcomes for both people and the planet. The window for action is narrowing, but significant change is still possible if states cooperate”says Bradshaw.
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As with any global-scale modeling, there are limits. There are too many evolving variables to account for, so these estimates must be viewed in the context of available data.
The concept of “carrying capacity” it also raises ethical issues: not all people have the same opportunities or consume the same resources, and discussions of population control are often sensitive and controversial.
“The tragedy is that human activity has interrupted the natural corrective mechanisms imposed by carrying capacity, without replacing them with humane and environmentally friendly corrective solutions”the authors conclude. The study was published in the journal Environmental Research Letters.
