Human Population Growthand its Implications

The human population is still growing nearlyexponentially. At the current rate of growththe human population on earth will reach10 billion in the first quarter of the next

century. Even if population control measureswere applied globally (and successfully), the

population would still reach 10 billion byaround 2050.

Events, times, and population sizes in human history: 1) Homo sapiens (us) first appeared somewhere

between 500,000 and 1,000,000 years ago.

2) By between 10,000 - 8,000 years ago the initialability to cultivate crops and domesticate someanimals had developed. Hunter-gatherers turnedinto farmers, with much more dependable sourcesof food. At this transition the total population wasabout 5 million.

3) Cities and towns developed, and were common byabout 3,000 years ago. By the time of Christ, thetotal population had grown to 130 million.

4) The plague hit first in 1348. It killed almost 4/5of the world’s population over the next ~100years. As is evident in the graph, recovery fromthis devastation was rapid.

5) Soon thereafter began the industrial revolutionand the growth of large cities. Before the outset of this revolution (1650 or so) the population had reached 500 million.

6) Early developments in medicine altered the deathrate. Industrial development provided the tools to increase food production. We reached 1 billion ~1850, having doubled in ~200 years

7) Growth from 1-2 billion occurred from 1850 to 1930, or over 80 years.

6) Doubling to 4 billion occurred by 1975. It took only 45 years.

8) We predict a doubling to 8 billion over only 35 years, with a current population of ~6.3 billion.

9) What has produced this growth? The birth rate hasremained nearly constant over the last 300 years.In fact it has declined slightly from 30/1000 peryear to 27/1000 per year. What has changed ismedicine and survivorship, so that there are nowabout 10 deaths/1000 per year. That calculatesout to a global growth rate of 1.8%/year.

There are two parts to the story of what we face interms of population size and distribution:

1) Population momentum - 20% of the human population today is less than 15 years old. Theyhave yet to begin reproducing in large numbers.Even if they only replace themselves, thehuman population will continue to increasethroughout their reproductive years (at least 25years), and the population will grow to morethan 10 billion in total. How much beyond maybe a critical question.

2) This population is not uniformly distributed overthe habitable parts of earth. By 2000, 60% ofthe human population will live in the tropicsand subtropics, almost all in UDCs (under-developed countries by the UN acronym).Even with population control in China, another20% will live there. Only 20% of humanslive in countries described as “developed”.

Associated with that is a reverse pattern in energyconsumption. About 80% of the energy (fossil fuel,industrial energy use) is used to support life in thedeveloped countries. Canada ranks right at the top -in addition to a fully developed “life style”, we livein a cold climate, adding immensely to fuel use forheating.

What about food?

Taking the U.N. FAO (Food and Agriculture Organization) standards for caloric intake necessaryto maintain moderate physical activity, the U.S., Canada, Russia (at least the text books includeRussia), Europe and Japan consume 25-33% more than needed. The UDCs (examples: Bangladesh, Kenya, Ecuador) consume 10-15% less than needed.Think about activity levels in these countries as well.

Now consider food production.

Malthus gave us the basic idea in 1798 (An Essay onthe Principle of Population):

Populations can grow exponentially, but food production increases only in a linear way. Eventuallythat leads to populations outstripping their resources.For Malthus that led to predictions of “misery andvice”.

Virtually all the land that can be cultivated undercurrent conditions is already in use. In the last century20% of the topsoil has been lost from those lands byerosion.

Energy subsidies make our way of life possible.A typical farm uses at least 10x the energy that isproduced in a natural area the same size, and produces less than twice the energy (products ofphotosynthesis) of an equivalent natural area.

Urban areas are much more heavily subsidized. Overall energy flow in an urban area is ~1000 timesthat in a natural area.

Can the situation be improved? To some extent, yes!

1) By utilizing native species that are frequently asnutritious as what we typically grow and eat.Examples: grain amaranths, winged bean

grain amaranths - fast growing, produce abundant grain rich in lysine (rare in plants, but essential in animal nutrition). Native in Latin America, particularly in highlands of Peru and Ecuador.

Winged bean - Psphocarpus tetragonolobus, nitrogen fixing, seeds, pods, and leaves all nutritious, as are potato-like tubers. You can sometimes find the pods in Oriental groceries.

2) By reducing dependence on chemical fertilizers and pesticides. Buzzwords: integrated pest management. One way - avoid monoculture, grow in mixed crop systems. That is the usual approach in traditional agriculture in some places, e.g.Thailand. The typical farm there grows coconuts (nitrogen-fixing, provides food and firewood), sugar palms, litchi nuts, harvests land crabs, and uses ponds to water ferns.

3) Through genetic engineering of crops - attempts to develop strains of some crop species that fix nitrogen, photosynthesize more efficiently (need less water, can use higher levels of sunlight, i.e., some of the characteristics of C4 photosynthesis), produce their own defenses against herbivore pests, and/or are resistant to herbicides used to control weeds that slow growth and reduce production. However, there is significant opposition to “GMO” crops.

These are just a few of the ideas being broughtforward to help support an increasing human population.

Humans have other impacts on the environmentbeyond the need of ever increasing numbers forfood. Among them are:

1) nuclear power and its implications

2) global warming from the burning of fossil fuels

3) acid precipitation

4) heavy metals and organic chemicals as poisons and pollutants

5) the ozone hole (fluorocarbons and their effects in the atmosphere)

Most of these concerns should be basically familiar.We’ll consider them to the extent time permits.

1) Nuclear power generationThere are advantages to nuclear power - a) it isn’t fossil fuel (no CO2 greenhouse gas) b) uranium fuel is not in danger of running out in the foreseeable future; c) the energy generating process has only one problematic waste product (heat), no acid gases, etc. produced by burning fossil fuel (no NOx, SO2) d) once the plant’s been built (very expensive) running it is not too expensive (but

provision for safety and end-of-life shutdown is expensive)

There are also disadvantages: a) Plants and their components age. Repair and replacement are expensive. Decommissioning plants is very expensive. b) How do we deal with waste fuel? No one has yet come up with a widely accepted solution. Fuel rods remain dangerously radioactive for ~1000 years. Present suggested disposal: bury the rods in very deep mines c) Chernobyl teaches us that safety concerns are critical. These concerns extend beyond proper operation to potential for sabotage.

The Three Mile Island nuclear power plant - an accident in 1979 released 17 curies of radioactivity.It was considered a disaster. Compare that toChernobyl.

Chernobyl as a case study indicates how extensivedamage can be:

1) >100 megacuries of radiation were released. This is far larger than released by the nuclear weapons exploded at Hiroshima or Nagasaki.2) Within 30km of the explosion, 24,000 people received doses of radiation that make them likely cancer victims.3) The radiation cloud spread over much of the hemisphere - initially over central Europe from Scandinavia to Greece, but later detectable in the western Northwest Territories.4) The likely result: from 5,000 to 75,000 cancer deaths due to the Chernobyl explosion.

A related, but lesser, pollution threat comes fromthe spread of radionuclides - radioactive materialsfrom atmospheric nuclear tests and various otherways in which radioactive materials are releasedand dispersed over the earth.

2) Global warmingGlobal warming is due to increases in so-calledgreenhouse gases in the atmosphere. Two arereadily identified and widespread: CO2 andmethane (CH4). Carbon dioxide concentrationin the atmosphere has risen for the last 200years, but mostly in the last 50 years.

Prior to the industrial revolution, CO2

concentration was 260-280ppm in the atmosphere. By 1958 it was 315ppm. By the early 1980s it was 340ppm. It is now 350-360 ppm.

Why is this important? When visible light enters the atmosphere, the air is nearly transparent to it. The light is absorbed by soil and living things. What they both release is heat, which is radiation in the infrared range of wavelengths. Infrared radiation is absorbed by greenhouse gases. Energy balance on earth is set by the balance between incoming and outgoing radiant energy. Temperatures on earth will increase (or are already increasing) as a result of increased “trapping” of infrared energy in the atmosphere.

The temperature change predicted based on trendsin fossil fuel use, etc. varies depending on what partof the globe you are considering.

Temperature change in the tropics may be only ~2C,

But in polar areas much larger changes are predicted, from 4 to 6C. These changes would partially to completely melt polar ice caps. Sea level would rise. Coastal areas and cities would be inundated.

Global weather patterns would change. Areas with the appropriate climates to grow important crops (wheat, rice, soybeans, corn) would shift. Poleward areas in North America don’t have appropriate soils to become “breadbaskets”.

3) Acid Precipitation The burning of fossil fuels, particularly oil in vehicles, releases nitrogen oxides (NOx) and sulfur oxides (SOx). These react in the atmosphere, forming nitric and sulfuric acids. They lower the pH of rainfall. That affects plant growth (agricultural productivity, forest growth) and affects the structural strength of buildings and statues. Limestone and marble, for example, are slowly dissolved by acid rain.

Notice the face of this Greek statue. It is being eaten awayby acid rain.

Fish cannot survive, nor can manyaquatic plants and small animals,at pHs <5. That’s the reasonlakes in the northeastern U.S.and Canada are so clear. Theyhave been acidified, and are nowbarren.

A related problem (i.e. related to fossil fuel combustion in vehicles) is the production of ozone. The mix of NOx, SOx, and ozone reacts in sunlight in the atmosphere at ground level to produce smog. We have smog alert days during the summer, but the problem is severe in the Los Angeles area, since it lies in a large scale “valley” that traps the mix and reaction productsin the area.

4) Heavy metal and organic pollutants

Heavy metals are widely dispersed, and are alsotoxic. The most important ones are lead, nickel,cadmium, and mercury.

Mercury causes Minimata disease (Lewis Carrollknew it as mad hatter’s disease). Lead causeslethargy and lowered mental development/performance.Cadmium poisons organs like the kidneys. All havebeen of local concern because of the Detroit wasteincinerator.

5) the ozone hole

A satellite image of the South Pole ozone hole

An ozone hole forms when fluorocarbons releasedfrom air conditioners and refrigerators react withozone in sunlight. The fluorcarbons are oxidized,using up the ozone.

Ozone absorbs UV light, protecting us from the harmful effects of penetrating radiation (DNA damage) that can cause a higher frequency of skin cancers.

There is a treaty that will decrease fluorocarbons in the upper atmosphere beginning soon (we hope). The treaty has taken effect; atmospheric improvements will take time. Currently the sizes of northern and southern ozone holes fluctuate from year to year.