28 June 2017
Leading Earth scientists suggest that human activity is having such a large impact on the planet that our presence will show up permanently in the geologic record. The International Commission on Stratigraphy is giving serious consideration to the idea that we are entering a new geologic epoch – the Anthropocene. In a 2016 article in Scientific American Jan Zalasiewicz, Chair of the Anthropocene Working Group, identified a number of human-created materials that would make distinctive geologic markers of the Anthropocene.
They include concrete, plastic, glass and pure aluminum, as well as chemical signatures such as increased levels of CO2 and nitrogen. One of the most compelling, for me – and one of the saddest – is the change in fossil assemblages. Zalasiewicz points out that humans now make up about one-third by weight of all large land vertebrates, while our domesticated animals make up almost all the rest; wild animals are less than 5 percent. Future palaeontologists will be able to quite clearly mark our presence and impact.
One of the key questions to be settled is when the Anthropocene began. A variety of dates have been suggested, but 1950 is gaining favour, and has been dubbed by some Earth scientists as the start of the Great Acceleration. This got me thinking, because I was born in 1948, so the major changes that constitute the Anthropocene have occurred in my lifetime. So what has happened in my lifetime?
In a 2017 article in The Anthropocene Review, Gaffney and Steffen summarised the rate of change for a number of key Earth systems since the 1950s, usually in comparison with the rate of change in the Holocene – the period since the end of the last Ice Age, about 11,000 years ago, until recently.
They reported the level of carbon dioxide in the atmosphere, the key driver of global warming, increased between 1970 and 2015 about 550 times faster than during the Holocene baseline, and “100 times faster than the most rapid rise during the last glacial termination”, when the glaciers were melting and the Ice Age was ending.
They also found that methane levels (another key greenhouse gas) were rising almost 300 times faster than the Holocene baseline, while global surface temperature is increasing 170 times faster. Between 1993 and 2010, sea levels were rising at about 3 mm per year (more than an inch a decade, about a foot per century) compared to zero from 3,000 years ago until the start of the industrial era; sea level is now higher than at any time in the past 115,000 years, and will continue to rise.
Other changes are equally alarming. The species extinction rate is estimated to be between 10 and 100 times the rate in the Holocene, while the rate of ocean acidification is estimated to be “70 times faster than during a deglaciation” and the “highest in possibly 300 million years”, and
humans “now fix as much nitrogen as all natural processes combined . . . possibly the largest and most rapid change to the global nitrogen cycle in 2.5 billion years”. A statistic I find quite compelling is that our mining activities now displace nearly three times more materials than do the Earth’s rivers.
All of these changes have taken place within a single human lifespan. What is driving them is an increase in human population and economic activity. Since my birth in 1948, according to data available through the International Geosphere-Biosphere Programme, the world’s population has increased about three-fold to 7 billion people, while the urban population has increased almost five-fold. Meanwhile, the world’s real GDP (in 2005 US dollars) has exploded 11-fold, from $4.5 trillion to more than $50 trillion in 2010.
Our primary energy use has increased 5-fold, as have the number of large dams, while water use has increased more than 3-fold. We catch more fish (4.6-times), lose more forest (1.7-times), consume more fertilizer (14-times) and produce more paper (5 times since 1961) than when I was born; the number of vehicles has increased 7-fold just since 1963 and international tourism arrivals have gone up 37 times.
This has been my life in the Anthropocene. Does anyone seriously think we can or should continue in this way?
© Trevor Hancock, 2017