Collapse: How Societies Choose to Fail or Succeed (90 page)
Read Collapse: How Societies Choose to Fail or Succeed Online
Authors: Jared M. Diamond
useless little fish or weed, like the snail darter or Furbish lousewort?" This
response misses the point that the entire natural world is made up of wild
species providing us for free with services that can be very expensive, and in
many cases impossible, for us to supply ourselves. Elimination of lots of
lousy little species regularly causes big harmful consequences for humans,
just as does randomly knocking out many of the lousy little rivets holding
together an airplane. The literally innumerable examples include: the role of
earthworms in regenerating soil and maintaining its texture (one of the rea
sons that oxygen levels dropped inside the Biosphere 2 enclosure, harm
ing its human inhabitants and crippling a colleague of mine, was a lack of
appropriate earthworms, contributing to altered soil/atmosphere gas exchange); soil bacteria that fix the essential crop nutrient nitrogen, which
otherwise we have to spend money to supply in fertilizers; bees and other insect pollinators (they pollinate our crops for free, whereas it's expensive
for us to pollinate every crop flower by hand); birds and mammals that dis
perse wild fruits (foresters still haven't figured out how to grow from seed
the most important commercial tree species of the Solomon Islands, whose
seeds are naturally dispersed by fruit bats, which are becoming hunted out);
elimination of whales, sharks, bears, wolves, and other top predators in the
seas and on the land, changing the whole food chain beneath them; and
wild plants and animals that decompose wastes and recycle nutrients, ulti
mately providing us with clean water and air.
4. Soils of farmlands used for growing crops are being carried away by
water and wind erosion at rates between 10 and 40 times the rates of soil
formation, and between 500 and 10,000 times soil erosion rates on forested
land. Because those soil erosion rates are so much higher than soil formation rates, that means a net loss of soil. For instance, about half of the top-soil of Iowa, the state whose agriculture productivity is among the highest
in the U.S., has been eroded in the last 150 years. On my most recent visit to
Iowa, my hosts showed me a churchyard offering a dramatically visible ex
ample of those soil losses. A church was built there in the middle of farm
land during the 19th century and has been maintained continuously as a
church ever since, while the land around it was being farmed. As a result of soil being eroded much more rapidly from fields than from the churchyard, the yard now stands like a little island raised 10 feet above the surrounding
sea of farmland.
Other types of soil damage caused by human agricultural practices in
clude salinization, as discussed for Montana, China, and Australia in Chap
ters 1, 12, and 13; losses of soil fertility, because farming removes nutrients
much more rapidly than they are restored by weathering of the underlying
rock; and soil acidification in some areas, or its converse, alkalinization, in
other areas. All of these types of harmful impacts have resulted in a fraction
of the world's farmland variously estimated at between 20% and 80% hav
ing become severely damaged, during an era in which increasing human population has caused us to need more farmland rather than less farmland.
Like deforestation, soil problems contributed to the collapses of all past so
cieties discussed in this book.
The next three problems involve ceilings
—on energy, freshwater, and
photosynthetic capacity. In each case the ceiling is not hard and fixed but
soft: we can obtain more of the needed resource, but at increasing costs.
- The world's major energy sources, especially for industrial societies,
are fossil fuels: oil, natural gas, and coal. While there has been much discus
sion about how many big oil and gas fields remain to be discovered, and
while coal reserves are believed to be large, the prevalent view is that known and likely reserves of readily accessible oil and natural gas will last for a few
more decades. This view should not be misinterpreted to mean that all of
the oil and natural gas within the Earth will have been used up by then. In
stead, further reserves will be deeper underground, dirtier, increasingly ex
pensive to extract or process, or will involve higher environmental costs. Of
course, fossil fuels are not our sole energy sources, and I shall consider
problems raised by the alternatives below. - Most of the world's freshwater in rivers and lakes is already being uti
lized for irrigation, domestic and industrial water, and in situ uses such as
boat transportation corridors, fisheries, and recreation. Rivers and lakes
that are not already utilized are mostly far from major population centers
and likely users, such as in Northwestern Australia, Siberia, and Iceland.
Throughout the world, freshwater underground aquifers are being depleted
at rates faster than they are being naturally replenished, so that they will
eventually dwindle. Of course, freshwater can be made by desalinization of
seawater, but that costs money and energy, as does pumping the resulting
desalinized water inland for use. Hence desalinization, while it is useful locally, is too expensive to solve most of the world's water shortages. The Anasazi and Maya were among the past societies to be undone by water
problems, while today over a billion people lack access to reliable safe drink
ing water.- It might at first seem that the supply of sunlight is infinite, so one
might reason that the Earth's capacity to grow crops and wild plants is also infinite. Within the last 20 years, it has been appreciated that that is not the
case, and that's not only because plants grow poorly in the world's Arctic regions and deserts unless one goes to the expense of supplying heat or water.
More generally, the amount of solar energy fixed per acre by plant photo
synthesis, hence plant growth per acre, depends on temperature and rain
fall. At any given temperature and rainfall the plant growth that can be supported by the sunlight falling on an acre is limited by the geometry and biochemistry of plants, even if they take up the sunlight so efficiently that not a single photon of light passes through the plants unabsorbed to reach
the ground. The first calculation of this photosynthetic ceiling, carried out
in 1986, estimated that humans then already used (e.g., for crops, tree plan
tations, and golf courses) or diverted or wasted (e.g., light falling on con
crete roads and buildings) about half of the Earth's photosynthetic capacity.
Given the rate of increase of human population, and especially of popula
tion impact (see point 12 below), since 1986, we are projected to be utilizing
most of the world's terrestrial photosynthetic capacity by the middle of this
century. That is, most energy fixed from sunlight will be used for human purposes, and little will be left over to support the growth of natural plant
communities, such as natural forests.
The next three problems involve harmful things that we generate or
move around: toxic chemicals, alien species, and atmospheric gases.
8. The chemical industry and many other industries manufacture or re
lease into the air, soil, oceans, lakes, and rivers many toxic chemicals, some
of them "unnatural" and synthesized only by humans, others present natu
rally in tiny concentrations (e.g., mercury) or else synthesized by living things but synthesized and released by humans in quantities much larger
than natural ones (e.g., hormones). The first of these toxic chemicals to
achieve wide notice were insecticides, pesticides, and herbicides, whose ef
fects on birds, fish, and other animals were publicized by Rachel Carson's
1962 book
Silent Spring.
Since then, it has been appreciated that the toxic ef
fects of even greater significance for us humans are those on ourselves. The
culprits include not only insecticides, pesticides, and herbicides, but also mercury and other metals, fire-retardant chemicals, refrigerator coolants,
detergents, and components of plastics. We swallow them in our food and water, breathe them in our air, and absorb them through our skin.
Often in very low concentrations, they variously cause birth defects, mental
retardation, and temporary or permanent damage to our immune and re
productive systems. Some of them act as endocrine disruptors, i.e., they in
terfere with our reproductive systems by mimicking or blocking effects of our own sex hormones. They probably make the major contribution to the steep decline in sperm count in many human populations over the last sev
eral decades, and to the apparently increasing frequency with which couples are unable to conceive, even when one takes into account the increasing average age of marriage in many societies. In addition, deaths in the U.S. from
air pollution alone (without considering soil and water pollution) are con
servatively estimated at over 130,000 per year.
Many of these toxic chemicals are broken down in the environment only
slowly (e.g., DDT and PCBs) or not at all (mercury), and they persist in the
environment for long times before being washed out. Thus, cleanup costs of
many polluted sites in the U.S. are measured in the billions of dollars (e.g.,
Love Canal, the Hudson River, Chesapeake Bay, the
Exxon Valdez
oil spill, and Montana copper mines). But pollution at those worst sites in the U.S. is
mild compared to that in the former Soviet Union, China, and many Third World mines, whose cleanup costs no one even dares to think about.
9. The term "alien species" refers to species that we transfer, intentionally
or inadvertently, from a place where they are native to another place where
they are not native. Some alien species are obviously valuable to us as crops,
domestic animals, and landscaping. But others devastate populations of native species with which they come in contact, either by preying on, parasitizing, infecting, or outcompeting them. The aliens cause these big effects
because the native species with which they come in contact had no previous
evolutionary experience of them and are unable to resist them (like human
populations newly exposed to smallpox or AIDS). There are by now literally
hundreds of cases in which alien species have caused one-time or annually
recurring damages of hundreds of millions of dollars or even billions of
dollars. Modern examples include Australia's rabbits and foxes, agricultural
weeds like Spotted Knapweed and Leafy Spurge (Chapter 1), pests and
pathogens of trees and crops and livestock (like the blights that wiped out American chestnut trees and devasted American elms), the water hyacinth
that chokes waterways, the zebra mussels that choke power plants, and the
lampreys that devastated the former commercial fisheries of the North
American Great Lakes (Plates 30, 31). Ancient examples include the intro
duced rats that contributed to the extinction of Easter Island's palm tree by
gnawing its nuts, and that ate the eggs and chicks of nesting birds on Easter,
Henderson, and all other Pacific islands previously without rats.
10. Human activities produce gases that escape into the atmosphere,
where they either damage the protective ozone layer (as do formerly wide
spread refrigerator coolants) or else act as greenhouse gases that absorb
sunlight and thereby lead to global warming. The gases contributing to
global warming include carbon dioxide from combustion and respiration, and methane from fermentation in the intestines of ruminant animals. Of
course, there have always been natural fires and animal respiration produc
ing carbon dioxide, and wild ruminant animals producing methane, but
our burning of firewood and of fossil fuels has greatly increased the former,
and our herds of cattle and of sheep have greatly increased the latter.
For many years, scientists debated the reality, cause, and extent of global
warming: are world temperatures really historically high now, and, if so, by how much, and are humans the leading cause? Most knowledgeable scien
tists now agree that, despite year-to-year ups and downs of temperature that
necessitate complicated analyses to extract warming trends, the atmosphere really has been undergoing an unusually rapid rise in temperature recently,
and that human activities are the or a major cause. The remaining uncer
tainties mainly concern the future expected magnitude of the effect: e.g.,
whether average global temperatures will increase by "just" 1.5 degrees
Centigrade or by 5 degrees Centigrade over the next century. Those numbers may not sound like a big deal, until one reflects that average global
temperatures were "only" 5 degrees cooler at the height of the last Ice Age.
While one might at first think that we should welcome global warming
on the grounds that warmer temperatures mean faster plant growth, it
turns out that global warming will produce both winners and losers. Crop
yields in cool areas with temperatures marginal for agriculture may indeed increase, while crop yields in already warm or dry areas may decrease. In
Montana, California, and many other dry climates, the disappearance of
mountain snowpacks will decrease the water available for domestic uses, and for irrigation that actually limits crop yields in those areas. The rise in
global sea levels as a result of snow and ice melting poses dangers of flood
ing and coastal erosion for densely populated low-lying coastal plains and
river deltas already barely above or even below sea level. The areas thereby
threatened include much of the Netherlands, Bangladesh, and the seaboard
of the eastern U.S., many low-lying Pacific islands, the deltas of the Nile and
Mekong Rivers, and coastal and riverbank cities of the United Kingdom
(e.g., London), India, Japan, and the Philippines. Global warming will also
produce big secondary effects that are difficult to predict exactly in advance
and that are likely to cause huge problems, such as further climate changes
