Thursday, September 15, 2011

Our ecological crises: Wake up and smell the stats

I'd like to put together a list of credible ecological statistics from reputable sources as a resource. Please post links to any such existing lists you are aware of or add any that have grabbed your attention (please make sure you include a source). To start us off, here are a few off the top of my head and in no particular order:
• Humans now affect over 80% of the world's land, 100% of the oceans and 100% of the atmosphere. Around 40% of the oceans have been "strongly affected" by our activities.

• Half of the world’s tropical forests have disappeared since World War II and roughly another 10 million hectares are being felled each year — the equivalent of 40 football fields every minute. The majority are being cleared by illegal loggers.

• Seventy-seven percent of global fisheries are fully exploited, over exploited or have been depleted. Based on 1998 data, the UN Food and Agriculture Organization estimates that global fishing fleets "are 2.5 times larger than needed."

• Marine apex predator numbers (i.e. large fish and sharks) have declined by 90% over the last 50-100 years, mainly due to overfishing (more stats on marine life decline). Another recent study put tuna decline at 60% in the last 50 years.

• Deep-sea trawling damages an area of sea bed twice the size of the contiguous USA each year.

• We're removing 9-10,000 tonnes of fish from the ocean every hour.

• As far as we can work out (and there are wide error margins on this one), species are currently going extinct at something like 100-1000 times the background rate of extinction, faster than at any time since the extinction of the dinosaurs 65 million years ago. It is likely that somewhere between 5,000 and 30,000 species become extinct each year. All the primary drivers of these trends are linked to human activities: land use changes, habitat destruction, pollutants, invasive species, anthropogenic climate change.

• Twenty-two percent of the world's plant species are threatened, and another 33% have an unknown status.

• Twenty-two species of Australian mammals become extinct between 1900 and 1960. Recently, mammal populations in Kakadu have gone into freefall.

• In the 1950s there were 450,000 lions worldwide and now there are only 20,000. Leopards are down from 700,000 to 50,000, cheetahs from 45,000 to 12,000 and tigers from 50,000 to just 3,000. And in the last forty years, elephant numbers have halved across protected areas in West and Central Africa. Globally, since 1970, wild vertebrate numbers have declined by almost one third.

• One study in 2001 put the annual cost of alien invasive species to the global economy at US$1.4 trillion annually, or about 5% of total GDP.

• Overall, current ecological damage is estimated to cost the global economy US$6.6 trillion annually (yes, with a "t").

• An area of arable land roughly the size of Greece or Nepal is lost to soil erosion and desertification each year. Since 1950, 1.9 billion hectares (4.7 billion acres) of land around the world has become degraded.

• By 1995, humans consumed 20% of global net terrestrial primary production. By 2005, it was 25%.

• Earth overshoot day occurs earlier each year. This is a notional measure designating the point in the year where global consumption exceeds the annual renewable biocapacity of the planet. In 2011, it falls on 27th September. Another way of saying this is that in 2010 the worldwide human population used about 135% of the resources the earth can generate in a year.

• Between 2000 and 2010, the number of cars and motorcycles in China increased twentyfold and there are now between 800 million and one billion cars in the world.

• As we burn 196,442 kilos of coal, 103,881,279 litres of natural gas and 150,179 litres of oil a second, we're dumping 62,500 tonnes of heat-trapping emissions into the earth's atmosphere every minute. Since the industrial revolution, we have increased the carbon dioxide in the atmosphere by more than 40% and increased the acidity of the oceans by 30% (a rate faster than anything seen before in Earth's history). The radiative forcing of the carbon dioxide human activities have put in the atmosphere is the equivalent of adding the energy of more than ten Hiroshima bombs every second and is likely the most significant contributing factor in Greenland losing around 9000 tonnes of ice every second (and accelerating), in about 90% of glaciers globally retreating, in precipitating the largest marine migration in two million years due to warming oceans and in ensuring that the last 318 consecutive months have had a global temperature above the 20th century average. The last month with below average temperatures was February 1985.

• Arctic summer sea ice has declined by 40% in extent and more than 75% in volume over the last three decades and 2011 saw new records for lowest extent and volume since records began. Due to increased summer melt, the fabled North West passage through the remote islands of Canada has been open to commercial shipping without icebreakers only four times in recorded history: 2011, 2010, 2008, 2007.

• Nearly 5.5 billion people (about 80% of global human population) live in an area where rivers are seriously threatened.

• The rate at which we are extracting groundwater has more than doubled between 1960 and 2000 and since 1960 18 trillion tonnes of water have been removed from underground aquifers without being replaced, enough to raise global sea levels by an average of 5 cm.

• In 1960, the Aral Sea was the world's fourth largest lake yet by 2000 it had shrunk to 20% of its original size due to over-irrigation on its feeder rivers.

• We put more than six million tonnes of plastic in the oceans annually, which is something like eight million pieces of litter each day, and over 119,000 items floating on every square kilometre of ocean.

• It is likely humanity has had a greater effect on the nitrogen cycle than any other phenomenon for the last 2.5 billion years.
Note that none of these are projections of present trends, they all relate simply to our present condition. This is currently an unsystematic sample; I have not (yet) tried to cover all of the various ecological and resource crises. This post may grow as I continue to gather more information.
I also posted some further statistics back here, though have not had a chance to post links to all the sources of those, and their credibility is something of a mixed bag.


Anonymous said...

Nice, Byron.

Toby said...

While we're talking on the other thread about acidity, I remembered that I wanted to mention a small error in this list, regarding the pH of the ocean.

Your source seems to have accidentally confused pH with the concentration of hydrogen ions. Although the hydrogen ion concentration is estimated to have gone up by 30%, that only results in a pH change from 8.25 to 8.14 (since pH is a negative logarithmic scale). So, summarizing it with "changed the pH of the oceans by 30%" is an error. has other citations for these numbers.

byron smith said...

Hi Toby, can I ask if this is Toby Hudson? Or if not, do you happen to be a chemist? I have done quite a bit of reading about ocean acidification and all kinds of reputable sources speak of the pH shift you mention as as comprising a 30% increase in acidity. Since the pH scale is logarithmic, then a shift from 8.25 to 8.14 is approximately 30%. I have not studied chemistry since I was 18, and am very happy to be corrected, but if I am in need of correction, then there seem to be more than a few published oceanic chemists who also need to be.

Toby said...

Hi Byron, yes it is Toby Hudson. It's ok to call it a 30% increase in acidity (or hydrogen ion concentration). But your summary says "changed the pH of the oceans by 30%". The [H+] may have changed by 30%, but that means the pH has only changed a little bit. If the pH changed by 30% (say from 8.25 to 5.775), that would already have been truly apocalyptic.

byron smith said...

Ah yes, I see. I my mistake. Thanks for picking it up. I'll modify the post.

byron smith said...

Soil stats from this UNEP report, summarised by Hot Topic: "since the 19th century, around 60 per cent of the carbon in the world’s soils and vegetation has been lost owing to land use. In the past 25 years, one-quarter of the global land area has suffered a decline in productivity and in the ability to provide ecosystem services because of soil carbon losses. Soil erosion associated with conventional agricultural practices can occur at rates up to 100 times greater than the rate at which natural soil formation takes place. Peatland drainage worldwide is causing carbon-rich peat to disappear at a rate 20 times greater than the rate at which the peat accumulated."

byron smith said...

IPCC AR4 WG2 §20.3.1 (2007): "Cultivated systems covered 25% of Earth’s terrestrial surface in 2000. On the way to achieving this coverage, global agricultural enterprises converted more area to cropland between 1950 and 1980 than in the 150 years between 1700 and 1850. As of the year 2000, 35% of the world’s mangrove areas and 20% of the world’s coral reefs had been lost (with another 20% having been degraded significantly). Since 1960, withdrawals from rivers and lakes have doubled, flows of biologically available nitrogen in terrestrial ecosystems have doubled, and flows of phosphorus have tripled. At least 25% of major marine fish stocks have been overfished and global fish yields have actually begun to decline."

byron smith said...

Tripati, Roberts, Eagle, 2009: "The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — [was about 15 million years ago and] global temperatures were 5 to 10 degrees Fahrenheit [3 to 6ºC] higher than they are today, the sea level was approximately 75 to 120 feet (22.5-36m) higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland."
(This quote is not directly from the paper, but is a summary of it offered by the lead author, and can be found here).

byron smith said...

DD: 11,000 sharks are killed every hour. That's three every second, or about 100 million each year. In the last twenty years, there has been something like a 90% decline in shark numbers.

byron smith said...

Guardian: Groundwater depletion has contributed more to recent sea level rise than any other factor.

byron smith said...

Telegraph: Great Pacific Garbage Patch has increased 100-fold since the 1970s.

byron smith said...

Mongabay: Tropical wildlife populations down by 61% over the last 48 years.

"These declines reflect large-scale forest and other habitat loss across these realms, driven by logging, growing human populations, and agricultural, industrial and urban developments," the report reads.

byron smith said...

DD: Rising dams - Number of free-flowing rivers.

"Of the approximately 177 rivers greater than 1,000km in length, only around a third remain free flowing and without dams on their main channel (WWF, 2006a)."

byron smith said...

Guardian: 50% decline in EU farm birds between 1980 and 2009, mainly due to agricultural policies.

byron smith said...

Guardian: "In the past 20 years, the world's environment has continued to deteriorate. According to the most recent Living Planet report, global demand for natural resources has doubled since 1996 and that is now 50% higher than the regenerative capacity of the planet.

"Meanwhile, carbon emissions have increased 40% in the past 20 years, biodiversity loss is accelerating and one in six people remain undernourished. Without a new path of development and a change in consumption patterns, the pressure on ecosystems and poor communities is set to intensity in the future as the global population is projected to rise from the current 7 billion to 9 billion by 2050."

byron smith said...

The Conversation: "WWF’s global Living Planet Index indicates that animal populations fell by 28% between 1970 and 2008. In Australia, more than 1,700 species and ecological communities are known to be threatened and at risk of extinction."

byron smith said...

IUCN: Only 4% of global species have been evaluated for extinction risk.

byron smith said...

BBC: Lemurs far more endangered than previously thought."That means that 91% of of all lemurs are assessed as being in one of the Red List threatened categories, which is far and away the largest proportion of any group of mammals,"

byron smith said...

Grist: The dark side of nitrogen.

byron smith said...

Guardian: UK bird numbers down by 20% since 1960s.

byron smith said...

Big cats, small space: Only 25% of the original African savannah remains undeveloped, leaving less and less room for the iconic megafauna that call it home.

byron smith said...

Guardian: Record algal blooms turn Yellow Sea green.

byron smith said...

Guardian: Peak water is the real threat to food security. Lester Brown with some alarming stats on the rate of groundwater depletion in key areas around the world.

byron smith said...

Independent: Elephants being wiped out.

"Up to 40,000 elephants, on average, are killed every year. That equates to one every 15 minutes. If that rate were to apply continuously, it would render the species extinct in the wild within 10 years. It is a tragedy, by any standard, that Africa has already lost some 90% of its elephants in the past half-century."

byron smith said...

Take Part: A paper published in Science (see here) "looked at 31 predator species and found three-quarters of them are in decline, including leopards, cheetahs, polar bears, tigers, giant otters, and multiple wolf species. The usual killer is loss of habitat from rapidly expanding human populations, combined with persecution by humans. [...] Over the past few decades, scientists have turned up increasing evidence that losing top predators can cause entire ecosystems to collapse, with humans among the potential victims."