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Biodiversity &monocultures

Scientists have only begun tounderstand the variety of lifethat exists on Earth.

Approximately 1.5 million species havebeen studied, but this is only a fraction ofthe species that are currently alive.

Biologists estimate the total number of livingspecies to be more than 5 million andperhaps as high as 50 million!

There is little doubt that most livingspecies have yet to be identified...

Canada is home to about 140,000 to200,000 species of plants and animals.Only 71,000 have been identified.

Biodiversity

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Biological diversity, or biodiversity, is thevariety of life found in an area.

Biodiversity is oftenmeasured by countingthe number of speciesin a specific habitat orecosystem.

Biodiversity

This measurement ofspecies numbers is calledspecies richness. A diverseecosystem will have highspecies richness.

Biodiversity

In general, species richness tends to behigher close to the equator.

Tropical rainforests have the highestbiodiversity of any ecosystem. Biodiversity

In a Peruvian rainforest, scientists identified283 tree species in a single hectare.

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A similar-sized deciduous forest in Ontariowould have fewer than 15 tree species.

The Amazon rainforest is home to more than200 species of hummingbirds, whereasOntario has only 1 species.

Imagine you are watching the burning of theworld’s greatest library. The building containsa copy of every book ever written.

Biodiversity Under Attack

Now imagine you are told that most ofthese books have never been read andthat no copies exist. Such a fire would bea tragic loss of human knowledge.

This scenario can be compared to thecurrent destruction of Earth’s biodiversity.

Many species are dying out,or going extinct.

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Their habitats are being destroyed throughdeforestation, urban and agriculturalexpansion, pollution and climate change.

Humans are rapidlydestroying Earth’secosystems withouteven knowing theirbiological contents.

Like the books inthe burning library,most of thesespecies have notbeen studied.

Extinction is anatural process.Over thousandsand millions ofyears, somespecies becomeextinct, while newspecies arise.

Biodiversity Under Attack

There have been at least five majorextinction events in the past 1 billion years.

Extinction events are usually caused by acatastrophic event such as an asteroidimpact or massive volcanic eruption.

Between such rare events, extinctionrates are very low.

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Unfortunately, human activity hasdrastically increased the rate of extinction.

When humans first encounter new species,they often overexploit them.

Biodiversity Under Attack

Within 200 years of theirarrival in New Zealand,humans had caused theextinction of 30 species oflarge bird, including 26species of giant moas.

About 80 species of mammalsand birds went extinct shortly afterhumans reached North America10,000 years ago.

Biodiversity Under Attack

The extinctions included saber-toothedtigers, mammoths, camels and horses, aswell as several ocean species such as theStellar’s sea cow.

Biodiversity Under Attack

In the past 400 years, over700 species of vertebrateshave become extinct.

12 species have becomeextinct in Canada in thepast 170 years.Unfortunately, the rate ofhuman-caused extinctionis increasing.

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Species at Risk

Species do not have to be driven toextinction for there to be ecologicalconsequences.

When a population’s size declines belowa critical level, the species will no longerbe able to fill its ecological niche.

This has consequences for the biotic andabiotic features of the ecosystem.

Species at Risk

For example, the lost of most (but not all)large sharks from a coral reef ecosystemchanges the food web and damages the reef.

Species at Risk

In Canada, the statusof species is monitoredby the Committee onthe Status ofEndangered Wildlife inCanada (COSEWIC).

Species at Risk

The committee has members fromgovernments, universities, otheragencies and Aboriginal peoples.

Experts on COSEWIC use the dataof species at risk to categorizethem into one of four categories:

Species at Risk

Species are classifiedas extirpated when theyno longer exist in thewild in a specific areabut still live elsewhere.

Frosted Elpin Butterfly

Species at Risk

Endangered species arethose that are in imminentdanger of going extinct orbecoming extirpated.

Wolverine

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Species at Risk

Threatened species are likely tobecome endangered if current trendsand conditions continue.

Humpback Whale

Species at Risk

Species of special concernmay become threatened orendangered because of acombination of factors.

• polar bear• red-headed woodpecker• Atlantic cod

157special concern

• humpback whale• wood bison• Kentucky coffee tree

146threatened

• barn owl• swift fox• northern cricket frog

238endangered

• paddlefish• Atlantic walrus

23extirpated

• great auk• passenger pigeon• sea mink

13extinct

Examples# of SpeciesClassification

Canadian Species at Risk When a species isplaced in theendangered orthreatened category,another agency calledRENEW (Recovery ofNationally EndangeredWildlife) prepares anaction plan to ensurethe recovery of thespecies.

We must act now to reduce habitat loss,urban expansion and pollution to protectEarth’s biodiversity.

Engineered Ecosystems

Engineered ecosystems cover a largeportion of Earth’s land area.

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As the human populationincreases, we replace naturalecosystems with land uses tosupport our modern lifestyles -e.g. farms (or “agroecosystems”),urban centres and roads.

The presence of non-native rather thannative species is just one way in whichfarmland, or agroecosystems, differs fromnatural ecosystems.

Engineered Ecosystems

In natural ecosystems, many speciesinteract, participating in and maintainingnatural cycles.

In agroecosystems, a verylimited number of speciesinteract and most cyclesare directly controlled oraltered by human activity.

Engineered Ecosystems

In general, when compared to naturalecosystems agroecosystems have moreuniform abiotic features, lower biodiversity,and are more intensively used by humans.

On agroecosystems farmers grow crops inmonocultures of non-native species whereonly one species is grown in a large field.

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In a monoculture, ecological cycles arealtered and biodiversity is reduced.

Engineered Ecosystems

Consumers that feed on crops areconsidered pests.

While natural systems sustain themselves overthousands of years, engineered ecosystemssuch as farmland must be managed.

Engineered Ecosystems

Farmers manage abiotic andbiotic conditions to maximizethe success of growingmonocultures.

They attempt to create idealand uniform growing conditionsand to eliminate competitors,diseases and pests.

Engineered Ecosystems

Ploughing, weeding, fertilizing,irrigating and the spraying ofpesticides are examples of suchmanagement techniques.

…but does the management of amonoculture result in a stable ecosystem?