Complexicon: Keystone Species

A keystone species is a species
that has a disproportionately

strong effect on the health and
functioning of its ecosystem.

Identifying and studying keystone species

can be useful in studying and
preserving the health of an ecosystem

Here's two examples of keystone species.

Reintroducing wolves
in the greater Yellowstone ecosystem

had cascading positive effects

on plant populations, on soil health,

in all the processes
that depend on both.

And restoring sea otters
along the Pacific Coast of North America

depressed populations of marine
herbivores and predators,

which allowed other species to recover.

Keystone species are
not just limited to charismatic mammals.

Effectively any organism
in an ecosystem could be keystone.

The critical characteristic
of a keystone species

is that a large portion of the flow of
energy and sources through an ecosystem

depends on that species.

This can occur when the species
consumes resources itself,

or promotes or inhibits the
consumption of resources by others.

Consider the north american
coastal redwood

Not only does this tree
provide raw sources of carbon

for other organisms to consume

it also alters the local climate.

Increasing moisture,
building organic rich soils

and providing a complex substrate

for other organisms to live in

from bryophytes to birds to insects to
microorganisms.

In effect, redwoods create
ecosystems within ecosystems

That's how highly connected they are
within the network of

all biological interactions
along the Pacific Coast

These species and many others
were discovered by accident

by misguided human actions
leading to their removal.

Resulting in negative downstream
consequences due to their absence.

But it doesn't have to be that way.

Tools from Network Science now allow us to
identify keystone species

using information about the interactions
that connect members of an ecosystem.

Such as when on spices feeds on another
or relies on another for its survival.

Using this network approach we don't have
to wait for the accidents to realize

what drives the ecosystem health.

Understanding keystone species
can help us explore ways

to restore biodiversity that sustains us.

And here, at the Santa Fe Institute
we'd like to apply concepts

across disciplinary boundaries so we can
use the idea of keystone species to

understand how innovations revolutionized
economy or how life itself began on earth.