Earth’s Carrying Capacity

PEAK OIL AND THEFATE OF HUMANITY

Mr. McCarthy’s adaptation of PEAK OIL AND THEFATE OF HUMANITYChapter 4 – The Fate of Easter IslandBy Robert Bériault

To start this story we have togo back in time to 500 AD…

to one of the most isolated places on Earth:

Easter Island.

Easter Island The land of the Moai

It was an uninhabited sub-tropical paradise 240 squaremiles

2300 milesfrom the

Chilean coast to

the east

1300 milesfrom the

Pitcairn Islandsto the west

A group of Polynesian settlers arrivedby boat around 500 AD

Archaeologistsestimate that therewere no more than100 people

The island wasknown as Rapa Nui

Large palm treesflourishedalong with 17species of other trees

These weresuitable formaking logs,planks anddugout canoes

They came equipped…They brought with them chickens, pigsand Polynesian rats.

They planted banana trees, taro root, andsweet potato.

The Islanders started to cut down the giant palms to build houses and dug-out canoes.

They supplemented their diet fromthe seaThere were no reefsaround Easter Island, andtherefore few small fish.

The main catch wasporpoises which theycaught from their largewooden canoes.

Conditions on the island made for aneasy life

They had timeon their handsfor religiousceremonies.

They held ceremonial dances and feasts

Stone mound for statues bases

… And they were expert stonecarvers

Building their statues was a monumental feat:

The statues weresculpted directlyfrom quarries in the sides of mountains

And were lugged as much as 14miles to theirplaces of honoralong the shore.

How big werethosestatues?

Partially completed statue abandoned in quarry

At first they only measured 8 to 12 feet high…

But competition built up between rival clans

The size of the statuesincreased in a spiral of one upmanship.

The last ones built were over 30 ft. high.

The biggest of allmeasured 70 feet andweighed 240 tons!

240 tons is the equivalent weight of 200 school buses

But withoutlevitation

machines howcould they have

transportedthem?

That question baffled researchers for a long time

But the consensus is that the Rapa Nui people built long slides out of timber leading to the ceremonial sites.

The statues would thenhave been placed on rollersmade from tree trunks andguided into place.

This statue movingactivity would havemade a significantcontribution todeforestation.

The Rapa Nui population grew

And bythe year1500…

Reached a peak of around 20,000

…there were 887 statues indifferent stages of completion.Hundreds of uncompletedstatues were simply abandonedin the quarries and their stonechisels were dropped on theground.

Shortlyafter, statuebuildingcame to anend…

All statue carving had stopped.

Someone had cut down the laststanding tree.

Only shrubs and grasses wereleft.

The population crash:

After the rich ground cover hadwashed away the springs dried up

There was a drastic dropin food production

The vast flocks of birdscoming to roost on theisland had disappeared

With no more wood…

They could no longerbuild replacement boats.Porpoise hunting, their main source of meat, came to an end.

They couldn’t rebuilddeteriorating homes – the Rap Nui resorted to living in reed huts and in caves.

They lost their mainsource of heating and cooking fuel.

Starvation was rampant

Fighting broke out over the diminishing food supply

Desperate, they even resorted to cannibalism

Winter temperatures were as low as 45°F. Withoutfirewood, everyone suffered.

Social order was in shambles. Vandals toppledrival clans’ statues

There was a massive die-off

Then came the Europeans:

It was on Easter Sunday of 1722Dutch Admiral Jacob Roggeveen arrived

He found 3000 people living in destitute conditions

Then 52 years later, Captain Cook visited the island

The only animals to be seen werechickens.

The warring clanswere in constantbattle

Over the next century:

Mostly due to contact with Europeans,the population plunged to a low of 111

Wow! How couldthat happen whenthe island had somuch to offer itspeople at thestart?

It’s simply that the Rapa Nui populationexceeded the island’s CARRYING CAPACITY

CARRYING CAPACITY is how manyorganisms a territory can supportindefinitely without degradation ofthe life support systems of thatterritory.

CARRYING CAPACITY OF THE EARTH

When it comes to humans, carrying capacity can be reduced by the type of food they chose.

For example, a meat diet requires much more land and energy input than a grain diet.It takes about 9 lbs of grain to produce one lbs of steak.So if a population decides it wants a meat diet, the carrying capacity would be less than if it were satisfied with a boring granola diet.

Lifestyle has an influence on CARRYING CAPACITY

All of these… …influence these PER CAPITA

Square feet of living space

Cars, RV’s, boats

Miles driven

Airplane, cruise ship andpleasure trips

Tools, electronics,Cookware, etc., etc.

Depletion of natural resources

Destruction of biodiversity

Future cropland compromised

Earlier Peak Oil

All of these effectsreduce carrying

capacity

A population can exceed the carrying capacity of its environment – what we call overshoot.

Overshoot becomes possible when a species encounters a rich and previously unexploited stock of resources that promotes its reproduction.

After apopulation overshoots,a massive die-off of thespecies follows.

St. Matthew IslandDuring WW2 the US CoastGuard released 29 reindeeron this remote island as aback-up food source fortheir men.Lichen mats 4 inches deepwhich had taken centuries togrow covered the island.Since there were nopredators, the food supplyallowed the reindeerpopulation to reach 6000 by1963.

Within three years of thereindeer having reached peak population, their numbers were slashed to 42 miserable, emaciated specimens.

The graph at the right showshow rapidly and sharply apopulation can crash when it overshoots.

Lichen is slow growing, so the carrying capacity was much less than 6000 reindeer.

Like the Easter Island peoples and the St. Matthew Island reindeer,

industrial age humans haveencountered a rich and previously

unexploited stock of resources thatpromoted their reproduction –

PETROLEUM!

The exploitation of oil is a one-shot affairthat enabled us to triple agricultural yields:

The vast amount of oil that Nature had put aside for us millions of years ago has artificially increased the Earth’s ability to provide us with food.

In other words, oilartificially tripledthe Earth’scarrying capacity.

How didoil dothis?

…How? Because oil provided the:

-resourcesto buildlaboratoriesandtechnologyto develophighyieldinggrains

- energyto run themachineryenablingonefarmer tofeed 100people

chemicalsto makefertilizersandpesticidesthustriplingyields

energyto pumpgroundwater forirrigation

energy totransportfood fromtheproducer totheconsumer

energyto drygrain andpreservefood, thuspreventinglargelosses

: All of these factors artificially increased food production –

temporarily.

Population Density--# of people per square mile

But when oil becomes rare, food production will plummet – just at a time when population is at its largest!

:

If we can’t convinceour government totake action, we maynot be able to bringrenewables on linefast enough…

…And if we have to resort to 19th centurytechnology, will we be able to feed ourgrowing population?

And if ever we had to resort to using drawanimals instead of tractors…

…then we’d need to develop 25 to 30% more croplandjust to grow thefeedstuffs to nourishthe animals.

The Easter Islanders nolonger had seaworthyvessels that wouldenable them to escapeto another island.They had no place togo.

…and neither do we.