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Natural communities are finely-tuned systems,
where each species has an
ecological
value to the other species that are part of that
ecosystem. Species diversity increases an ecosystem'sstability and resilience, in particular its ability to adapt and
respond to changing environmental conditions. If a certain amount,or type (such as a keystone species) of species are lost,
eventually it leads to the loss of ecosystem function. Manyecosystems though have built-in redundancies so that two or more
species' functions may overlap. Because of theseredundancies, several changes in the number or type of species may
not impact an ecosystem. However, not all species within anecosystem are of the same importance. Species that are important
due to their sheer numbers are often called
dominant species . These species make up the
most biomass of an ecosystem. Species that have importantecological roles that are greater than one would expect based on
their abundance are called
keystone
species . These species are often central to the structure
of an ecosystem, removal of one or several keystone species mayhave consequences immediately, or decades or centuries later
(
Jackson
Kelp forests, as their name suggests, are dominated by kelp, a brown seaweed of the family Laminariales.They are found in shallow, rocky habitats from temperate to subarctic regions, and are important ecosystems for manycommercially valuable fish and invertebrates.
Vast forests of kelp and other marine plants
existed in the northern Pacific Ocean prior to the 18thcentury. The kelp was eaten by herbivores such as sea urchins
(Family Strongylocentrotidae), which in turn were preyed uponby predators such as sea otters (
More recently sea otter populations in Alaska
seem to be threatened by increased predation from killerwhales (
Interestingly, a similar scenario in kelp
forests in Southern California did not show immediate effectsafter the disappearance of sea otters from the ecosystem. This
is because the system was more diverse initially. Otherpredators (California sheephead fish,
In the 1970s and 1980s, a sea urchin fishery developed which then enabled the kelp forest torecover. However, it left a system with little diversity. The interrelationships among these species and the changes thatreverberate through systems as species are removed are mirrored in other ecosystems on the planet, both aquatic andterrestrial.
As this example illustrates, biodiversity is incredibly complex and conservation efforts cannot focus onjust one species or even on events of the recent past.
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