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Testing, testing, one, two, three.
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When your band is trying to perform,
feedback is an annoying obstacle,
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but in the grand orchestra of nature,
feedback is not only beneficial,
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it's what makes everything work.
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What exactly is feedback?
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The key element, whether in sound,
the environment or social science,
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is a phenomenon called
mutual causal interaction,
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where x affects y, y affects x, and so on,
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creating an ongoing process called
a feedback loop.
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And the natural world is full
of these mechanisms
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formed by the links between living
and nonliving things
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that build resilience by governing
the way populations
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and food webs respond to events.
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When plants die, the dead material
enriches the soil with humus,
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a stable mass of organic matter,
providing moisture and nutrients
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for other plants to grow.
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The more plants grow and die,
the more humus is produced,
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allowing even more plants to grow,
and so on.
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This is an example of positive feedback,
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an essential force
in the buildup of ecosystems.
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But it's not called positive feedback
because it's beneficial.
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Rather, it is positive because it amplifies
a particular effect or change
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from previous conditions.
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These positive, or amplifying, loops
can also be harmful,
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like when removing a forest
makes it vulnerable to erosion,
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which removes organic matter
and nutrients from the earth,
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leaving less plants to anchor the soil,
and leading to more erosion.
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In contrast, negative feedback diminishes
or counteracts changes in an ecosystem
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to maintain a more stable balance.
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Consider predators and their prey.
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When lynx eat snowshoe hares,
they reduce their population,
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but this drop in the lynx's food source will
soon cause their own population to decline,
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reducing the predation rate and allowing
the hare population to increase again.
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The ongoing cycle creates an up and down
wavelike pattern,
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maintaining a long-term equilibrium and
allowing a food chain to persist over time.
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Feedback processes might seem
counterintuitive because many of us
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are used to more predictable linear
scenarios of cause and effect.
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For instance, it seems simple enough that
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spraying pesticides would help plants grow
by killing pest insects,
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but it may trigger a host of other
unexpected reactions.
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For example, if spraying pushes down
the insect population,
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its predators will have less food.
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As their population dips,
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the reduced predation would allow the
insect population to rise,
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counteracting the effects of
our pesticides.
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Note that each feedback is
the product of the links in the loop.
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Add one negative link and it will
reverse the feedback force entirely,
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and one weak link will reduce the
effect of the entire feedback considerably.
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Lose a link, and the whole loop is broken.
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But this is only a simple example,
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since natural communities consist not
of separate food chains,
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but networks of interactions.
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Feedback loops will often be indirect,
occurring through longer chains.
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A food web containing twenty populations
can generate thousands of loops
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of up to twenty links in length.
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But instead of forming a disordered
cacophany,
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feedback loops in ecological systems
play together,
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creating regular patterns
just like multiple instruments,
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coming together to create a complex
but harmonious piece of music.
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Wide-ranging negative feedbacks
keep the positive feedbacks in check,
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like drums maintaining a rhythm.
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You can look at the way a particular
ecosystem functions within its unique habitat
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as representing its trademark sound.
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Ocean environments dominated
by predator-prey interactions,
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and strong negative and positive loops
stabilized by self-damping feedback,
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are powerful and loud,
with many oscillations.
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Desert ecosystems, where the
turn over of biomass is slow,
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and the weak feedbacks loops through dead
matter are more like a constant drone.
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And the tropical rainforest,
with its great diversity of species,
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high nutrient turnover, and strong feedbacks
among both living and dead matter,
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is like a lush panoply of sounds.
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Despite their stabilizing effects,
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many of these habitats and their
ecosystems develop and change over time,
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as do the harmonies they create.
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Deforestation may turn lush tropics
into a barren patch,
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like a successful ensemble breaking up
after losing its star performers.
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But an abandoned patch of farmland
may also become a forest over time,
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like a garage band growing into
a magnificent orchestra.
Ariana Bleau Lugo
4:07 ...constant drum | x ...constant drone ?
Ariana Bleau Lugo
4:07 Mea culpa. I think it is indeed drone.