the

The World is Green (Hairston, Smith and Slobodkin 1960)

the world is green but why is the world

green on land plants stand tall and

Trevi lush and grassy thick and scrubby

but the land is also full of hungry

herbivores chewing gnawing slurping and

sniffing so what keeps these consummate

consumers from nibbling down every last

leaf what keeps any population in check

even Darwin knew that populations must

be limited or even the slowest tortoise

could eventually overrun the earth with

its plotting progeny but just how these

carrying capacities are set has been

hotly debated is it density dependence

or a matter of climate for the good of

the species well you see when sunlight

hits the earth much of its energy is

photosynthetically transformed into

plants then into animals and then

someday a lump of carbon in the soil but

we don't find ourselves awash in a sea

of detritus and drowning in fossil fuel

all this waste this trash is their

treasure food that they process into new

little bodies and return as nutrients to

the soil rather than letting it be

packed into the earth as oil if

composers were limited by predators or

climate there would be lots of extra

food around but the fact that oil is

rare means that food must be set in

their life further up the trophic chain

plants compete for a plot of soil to

take up nutrients and a patch of

sunlight in which to grow for plants

space is the limiting resource and they

fight viciously to keep it plants are

then preyed upon by herbivores which in

turn becomes the prey themselves

predators and parasites limit herbivore

populations leave in the world of green

plants and a diversity of herbivores

more concerned with escape than

starvation the carnivorous predators on

the other hand compete fiercely for food

that is difficult to catch the effort

required to keep a full belly means that

only a small number of carnivores can

persist in any population the best

evidence for this pattern comes when the

chain is broken when we remove

carnivores herbivores are Unleashed

to munch up all those plants sometimes

eating themselves right out of resources

with herbivores limited by food alone

the world becomes a very different color

so what we see in the world around us

can illuminate the unseen that different

trophic levels must be regulated by

different processes

you