An Ecologically Stressed Planet
“From an ecological systems
perspective, callously pushing
other species to extinction
is akin to foolishly sawing
off the limb on which
humanity itself perches.”
At the top of the list of human activities that negatively impact ecosystems is agriculture. This is not surprising as it is the largest interface between humans and the environment.
Land conversion destroys habitat, increases soil erosion, and accelerates loss of species diversity.
About 12 percent of our current land surface is under crop cultivation. Much of this land degrades over time, and we are already exceeding the regenerative capacity of the Earth’s soil resources.
Approximately 40 percent of cultivated land is experiencing soil erosion, reduction in fertility, or overgrazing.
Soil loss rates exceed soil formation rates by at least tenfold.
The conversion of land in the Amazon rainforest for cattle ranching and for feed could tip the basin into an irreversible transformation to a semi-arid savanna that in turn triggers unpredictable changes to the global climate system.
Rates of habitat destruction and of species extinction have led to the sixth major extinction event in history — and the first one to be caused by human activity.
A majority of the world’s most species-rich habitats — such as tropical forests and coral reefs — have been destroyed or are being significantly impacted.
The extinction rate has increased to 100 to 1,000 times that of normal background levels. It is projected to increase another tenfold before the end of this century.
Much of the recent extinctions have occurred on the main continents from land-use changes, introduction of invasive species, and climate change.
Insects are globally dying en masse, risking a catastrophic collapse of Earth’s delicate, interdependent ecosystems that could present a real existential threat to the survival of human civilization. This alarming insect apocalypse is being driven by habitat loss because of intensive agriculture, the heavy use of pesticides, climate change, and invasive species.
More than 40 percent of insect species are dwindling globally and a third of species are endangered. The total mass of insects is falling by 2.5 percent annually.
If the decline continues at this rate, insects could be wiped off the face of the Earth within a century. The proportion of insects in decline is currently twice as high as that of vertebrates and the insect extinction rate is eight times faster than that of mammals, birds, and reptiles.
Insects play a profoundly important role in Earth’s ecosystems. They are a food source for many animals, critical pollinators, and recyclers of nutrients back into the soil.
A world with no insects would likely be a flowerless world of collapse or decay and erosion and a loss that would spread quickly through ecosystems.
It would be a less vibrant world of silent and still forests and a less appealing world of dung and old leaves and rotting carcasses accumulating in cities and roadsides.
The biomass of wild animals has been catastrophically reduced, especially over the past 10,000 years, while human and livestock numbers have skyrocketed.
By mass, humans and domesticated livestock now make up 97 percent of all animals on land. Wild mammals and birds (elephants, mice, kangaroos, lions, raccoons, bats, bears, deer, wolves, moose, chickadees, herons, eagles, etc.) have been reduced to a mere 3 percent.
The biomass of chickens (livestock) alone is more than double the total mass of all other birds combined.
Before the advent of agriculture 10,000 years ago, humans made up just a tiny fraction of animal biomass, and domesticated livestock did not exist.
Since 1950 we've wiped out around 90 percent of the big fish in the ocean — swordfish, marlin, and grouper.
What does it say that just one bluefin tuna can bring $180,000 on the Japanese market.
Upwards of 270,000 sharks are killed each day, mostly for their fins, which bolster the status of the soups they are destined for.
Every year, an undersea area twice the size of the continental United States is plowed with trawlers leveling everything on the sea floor.
The extinction rate that humans are now causing has not been seen since the Cretaceous–Paleogene extinction event 65 million years ago when an asteroid impact wiped out the dinosaurs.
The collective human impact on biodiversity increasingly resembles, in fact, a slow-motion asteroid impact on the planet.
Unless we reduce the scale and impacts of human societies and economies, and unless we more equitably share the Earth with wild species, we will fully enter another major global extinction event — only the sixth in over 500 million years.
Losses of certain keystone species make terrestrial and aquatic ecosystems more brittle and vulnerable to even slight changes in climate and ocean acidity.
Tragically, biodiversity is not adequately protected because its value is not included in the market signals that guide the economic decisions of producers and consumers and dictate the overall operation of the economic system.
From an ecological systems perspective, callously pushing other species to extinction is akin to foolishly sawing off the limb on which humanity itself perches.
Another grave concern is ocean acidification.
The oceans, covering 70 percent of the planet's surface, currently absorb about 25 percent of human-emitted carbon dioxide through dissolution into the seawater and through uptake of carbon by marine organisms. The portion of this carbon dioxide that turns into carbonic acid has the destabilizing side effect of increasing the acidity (reducing the pH) of surface seawater, making it more corrosive and threatening to normal ecosystem functionality.
The rate of ocean acidification is at least 100 times faster than at any time in the last 20 million years, and surface ocean pH has decreased by about 0.1 units relative to pre-industrial times.
Corals are sensitive to pH levels and warming waters, and stressed reefs are undergoing negative shifts in dynamics, productivity, and species composition.
Marine plankton are also vulnerable and would affect the food chain all the way up. As water acidifies, the small phytoplankton at the very base of the planet's food chains struggle to form carbonate for their skeletal parts.
Though we are naturally more aware of the destabilizing climate-change effects of the extra heat in the atmosphere around us resulting from fossil fuel combustion, over 90 percent of the additional heat is, in fact, absorbed by the sea.
The deep sea is now warming about nine times faster that it was in the 1960s, '70s, or '80s.
It has been estimated that, without the massive watery heat sink capacity of the world's oceans, the average air temperature around the globe would already have increased by a staggering 97 degrees Fahrenheit.
Record-breaking temperatures from a changing climate have damaged more than two-thirds of the Great Barrier Reef — the largest living structure on Earth.
The potent combination of warming and acidifying water has resulted in more and more mass coral reef bleaching events around the globe. Though they only take up a very small area in the world's oceans, coral reefs are home to a quarter of all marine species.
Already half of the world's coral reefs have been lost over the last thirty years.
Ocean scientists, in a 2013 report to the United Nations, expressed their worry that by 2050, virtually all of he world's coral reefs could be dead. And by the end of the century, we will have indeed turned the sea the into a very harsh 'hot, sour, and breathless' habitat for the remaining marine life.
Peak fish may have occurred in 1996, as global marine catches have been declining ever since.
With unsustainable business-as-usual commercial fishing practices, one science journal predicts that the oceans will be commercially fished by 2048.
More heat in the atmosphere turns up the dial on the hydrologic cycle with rising rates of water storage and circulation in the atmosphere producing drier droughts and wetter floods around the globe.
Cyprus and other countries in the eastern Mediterranean, for example, are increasingly vulnerable to drought as the changing climate brings higher temperatures and less precipitation. These conditions invariably lead to mass migrations of climate refugees inevitably followed by social and political instability from clashing populations.
Groundwater aquifer depletion from expanding human populations and from competition for water resources is threatening the long-term economic viability of agricultural regions.
Hydrological poverty occurs when food production is artificially inflated by unsustainable practices of mining for groundwater. This creates a dangerous food-bubble economy.
Also, almost all of the world's rivers have been altered, and about 25 percent of global river flows no longer reach the ocean due to these river-flow diversions.
These dramatic reductions of global freshwater supplies affect not only the biodiversity of river systems, but also the food sources, health, and security of local communities, climate regulation, and carbon sequestration. Tipping points may be reached that result in the collapse of regional hydrologic cycles.
Eutrophication, a special case of environmental pollution, is the sudden unintended introduction of very high levels of nutrients into formerly lower nutrient systems.
Human agricultural runoffs of nitrogen and phosphorus, for example, have caused abrupt shifts in lakes and marine ecosystems where the species of primary producers adapted to the lower nutrient conditions are outcompeted by faster growing species adapted to the anomalous high-nutrient conditions.
The suddenness of the shift only affects the primary producers, resulting in a disorganized and out-of-balance collection of species with much internal disruption — like plankton blooms and mass fish die-offs.
Human activities now convert more nitrogen from the atmosphere into reactive forms — mostly to enhance food production via fertilizers — than all of the Earth’s terrestrial processes combined. The majority of it ends up in waterways and coastal zones.
The inflow of phosphorus into oceans exceeds natural background levels by eight to nine times and may be the key driver behind global-scale anoxic events causing dead zones of marine life.
Chemical pollution includes radioactive compounds, heavy metals, and a wide range of organic compounds of human origin.
Toxic chemicals represent a form of unnatural, human-made pollution that no existing natural systems have experienced before and that no existing natural systems can benefit from in a positive way.
Out of some 80,000 chemicals in commerce, 1,000 are known to be neurotoxic in experiments.
Different chemicals have different pathways through Earth’s biosphere.
Some, such as mercury or DDT, can undergo long-range transport via ocean or atmospheric dynamics.
Chronic, low-dose exposure may lead to subtle non-lethal effects that hinder development, disrupt endocrine systems, impede reproduction, or cause mutagenesis. These are usually most visible in top predators and human populations.
Sadly, it is difficult to find a sample of ocean water with no sign of some chemical pollution as polychlorinated-biphenyls (PCBs), other persistent toxic chemicals such as DDT, and heavy metal compounds continue to accumulate throughout the world's widely dispersed marine ecosystems.