As the human population has tripled in the last 60 years, Earth has suffered greatly from the ever-increasing demands we’ve been making on the planet’s resources. We have developed the technology to over-fish the seas, cut down the rain forests and convert all but the most inhospitable landscapes for our own use. Do we have the wisdom to slow down our consumption of natural resources before it’s too late?
Having passed my 60th birthday last year, I am now the oldest professor in my university department. I can remember decades like the 1950s and 1960s that others have only read about. Since I lecture classes on biological conservation, I tell my students about what life was like when the world was less crowded than it is now. This isn’t just nostalgia. The shocking truth is that the world’s human population has tripled in my lifetime.
Figure 1. History of the growth of human population since 1750. Data from the U. S. Census Bureau, 2015.
No one living at any other time in history could say that. In the year AD 1, the total human population was somewhere between 170 and 400 million. It took 1800 years for the world’s population to reach 1 billion people. Then it doubled to 2 billion in just 130 years (1930). It’s more than tripled since then, and now stands above 7 billion people. As the population grew, so did our consumption of the world’s resources. This, fundamentally, is at the heart of all the global change impacts on the planet. As editor-in-chief of the online Reference Module in Earth Systems and Environmental Sciences, I am also in a fairly unique position of being able to keep current on the whole suite of environmental issues affecting our planet.
The review articles in this module are all written by experts in their respective fields, and vetted by other experts (what’s known as the peer-review system) to ensure their accuracy. This may seem like standard operating procedure, but that is far from being the case these days, when it comes to on-line publications. The worldwide web has provided us with overwhelming amounts of information, but the content of web sites, especially sites devoted to topical issues such as conservation, ranges from highly accurate and reliable texts written by scholars to misinformation written by crackpots or political ideologues. So it is important for the scientific community to have access to trustworthy information, written by experts and backed up by qualified reviewers. The other advantage of producing an on-line reference module is that we are updating it month by month, as new scientific discoveries are being made. The combination of accuracy and immediacy gives authenticity to our articles.
It takes an incredible amount of the world’s resources just to feed our species. Biologists measure the vigour and productivity of a landscape in terms of primary productivity – the growth of plant life in a region. This varies from very high levels in the wet tropics to low levels in deserts and arctic tundra. Humans have now appropriated between 25% and 38% of the entire world’s net primary productivity for their own use, mainly for agriculture. This robs ecosystems of their natural resources, forcing many species to extinction. Extinction rates are now as much as 1000 times the expected background rate. Natural ecosystems are becoming a rarity in the developed parts of the world. This greatly reduces or destroys the habitats for the species that live in these ever-shrinking ecosystems, driving them towards extinction. Habitat conversion to human use exceeds habitat protection by a ratio of 10:1 in more than 140 of the world’s ecoregions. The areas that had already lost more than half of their natural habitats by the middle of the 20th century include the Mediterranean region, temperate forests and grasslands (especially in Europe and North America), and tropical/subtropical dry broad-leaved forests.
Figure 2. History of habitat losses in major biomes. Data from Primack, 2006.
The latter region is one of the easiest of the tropical regions to convert to agriculture or animal husbandry. The ecosystems under threat in the coming decades include tropical and subtropical grasslands and savannahs and tropical and subtropical coniferous forests. If nothing is done to protect these regions from development, then more than three-quarters of the landscapes in these ecosystems are predicted to suffer severe human impacts by the year 2050.
Habitat loss is probably the single greatest threat to terrestrial species today. The process is often irreversible, as once natural habitats have been lost to human use, they are seldom returned to a natural condition. As increasingly greater areas are lost or fragmented, the possibility of species migration from one patch of natural habitat to another decreases proportionally. Of course, some organisms are better dispersers than others. Fragmentation limits potential dispersal and colonization by creating barriers to movement. Animals of the forest interior will not cross open ground. Thus, an agricultural field that is 100 m wide may form an impassable barrier to species in adjacent forests, such as deer. When the heads of nations have met to discuss strategies to save the planet, such as the UN Summit meetings in Rio de Janeiro (1992), Kyoto (1997), and Copenhagen (2009), the focus has been on limiting greenhouse gas emissions. Of course this is an important issue, but habitat destruction has been so far down the list of priorities that it scarcely gets mentioned in the press releases. And yet in terms of importance for preserving the biological diversity and ecological health of the planet, it ought to be our number one concern. Instead, it seems to be the elephant in the room- the one that never gets mentioned when the family of the world’s nations gets together. Who would propose turning farm land back to forest or deconstructing cities to restore a native grassland?
The overexploitation of Earth’s resources has developed alongside the burgeoning human population, in conjunction with rising standards of living. This overuse of the planet’s resources has been documented by the Global Footprint Network, in terms of the ecological footprint of each of the world’s nations. Because of the highly variable standards of living in the world, some nations are using up natural resources and producing waste products at far higher rates than others. One measure of this is the number of hectares of land per person it takes to sustain the lifestyle of the average person in a given country. Relatively poor countries, such as India, require an average of 0.9 ha per person to sustain their current standard of living. Relatively rich countries, such as those of western Europe and North America, require between about 4 and 8 ha of land per person to sustain their standard of living.
Figure 3. The current ecological footprint of various countries, expressed by the number of hectares of land required to sustain the current standard of living in that country. Data from the Global Footprint Network (2015).
This overexploitation of the planet’s resources can be summed up as follows. We currently need the resources equivalent of 1.5 planets to provide the resources we use and absorb our waste. United Nations scenarios for moderate growth suggest that if current population and consumption trends continue, by the 2030s, we will need the equivalent of two Earths to support us. This level of resource consumption is obviously unsustainable. There is no Planet B we can inhabit, anytime in the near future.
Dear old planet Earth is straining under the weight of human impacts –struggling to supply all our needs for food, clean water, breathable air, and unpolluted soils. Our species has been intelligent enough to figure out ways of harnessing the planet’s resources for our own uses. We have brought industrial power to bear on highly mechanized agriculture, the clearing of forests, the harvesting of fish from the world’s oceans, the production of chemical fertilizers – the list goes on and on. But are we bright enough to acknowledge that the current rate of exploitation of the planet’s resources is unsustainable? Perhaps more to the point, do we have the political will to make the necessary changes in the way we do things? In my view, we cannot leave this to the politicians. Even with the best will in the world, the primary goal of elected officials is to win the next election. This is rarely achieved by telling the voters things they may not like to hear. It takes a very brave politician to tell the electorate that they must cut back on their consumption of the world’s resources. This kind of message forces us to consider lifestyle change. As such, the message has to come from the bottom-up. There must be a groundswell of public opinion to get action at the national and international level. I hope that by keeping a finger on the pulse of the planet, our reference module will help inform the scientific community, so that we can do our part in raising peoples’ conservation consciousness. Ultimately, the decisions are up to them.
Scott A. Elias grew up in Colorado, USA, and received both an undergraduate degree (1976) and PhD (1980) in environmental biology from the University of Colorado. His PhD dissertation concerned paleoenvironmental reconstructions of Holocene insect fossil assemblages from two sites in arctic Canada. He went on to do postdoctoral fellowships at the University of Waterloo, Canada, and the University of Bern, Switzerland. Scott returned to the University of Colorado in 1982 and became a research associate of the Institute of Arctic and Alpine Research. He remained there for the next 18 years, becoming a fellow of the institute, before departing for England to take up a lectureship in physical geography at Royal Holloway, University of London, where he remains, today.
Scott became professor of Quaternary science in 2007, following the publication of the Encyclopedia of Quaternary Science that same year. He continues to do research in Quaternary insect fossils, having studied fossil assemblages from more than 175 localities in North America and Europe. The focus of much of his research has been in Beringia: the regions of the Yukon Territory, Alaska, and northeastern Siberia that were linked together by the Bering land bridge during glacial intervals of the Pleistocene. Scott has authored or edited 10 books and 130 journal articles and book chapters. He has now taken on the role of editor-in-chief of Elsevier’s online reference module: Earth Systems and Environmental Sciences.