B2 中高級 美國腔 16181 分類 收藏
Our planet's diverse thriving ecosystems may seem like permanent fixtures,
but they're actually vulnerable to collapse.
Jungles can become deserts,
and reefs can become lifeless rocks,
even without cataclysmic events, like volcanoes and asteroids.
What makes one ecosystem strong and another weak in the face of change?
The answer, to a large extent, is biodiversity.
Biodiversity is built out of three intertwined features:
ecosystem diversity,
species diversity,
and genetic diversity.
The more intertwining there is between these features,
the denser and more resilient the weave becomes.
Take the Amazon rainforest,
one of the most biodiverse regions on Earth
due to its complex ecosystems,
huge mix of species,
and the genetic variety within those species.
Here are tangled liana vines,
which crawl up from the forest floor to the canopy,
intertwining with treetops
and growing thick wooden stems that support these towering trees.
Helped along by the vines,
trees provide the seeds, fruits and leaves to herbivores,
such as the tapir and the agouti,
which disperse their seeds throughout the forest so they can grow.
Leftovers are consumed by the millions of insects
that decompose and recycle nutrients to create rich soil.
The rainforest is a huge system filled with many smaller systems, like this,
each packed with interconnected species.
Every link provides stability to the next,
strengthening biodiversity's weave.
That weave is further reinforced
by the genetic diversity within individual species,
which allows them to cope with changes.
Species that lack genetic diversity due to isolation
or low population numbers,
are much more vulnerable to fluctuations
caused by climate change, disease or habitat fragmentation.
Whenever a species disappears because of its weakened gene pool,
a knot is untied and parts of the net disintegrate.
So, what if we were to remove one species from the rainforest?
Would the system fall apart?
Probably not.
The volume of species,
their genetic diversity,
and the complexity of the ecosystems
form such rich biodiversity in this forest
that one species gap in the weave won't cause it to unravel.
The forest can stay resilient and recover from change.
But that's not true in every case.
In some environments, taking away just one important component
can undermine the entire system.
Take coral reefs, for instance.
Many organisms in a reef are dependent on the coral.
It provides key microhabitats, shelter and breeding grounds
for thousand of species of fish, crustaceans and mollusks.
Corals also form interdependent relationships with fungi and bacteria.
The coral itself is a loom
that allows the tangled net of biodiversity to be woven.
That makes coral a keystone organism,
one that many others depend on for their suvival.
So what happens when destructive fishing practices,
pollution and ocean acidification
weaken coral or even kill it altogether?
Exactly what you might think.
The loss of this keystone species leaves its dependents at a loss, too,
threatening the entire fabric of the reef.
Ecosystem, species and genetic diversity
together form the complex tangled weave of biodiversity
that is vital for the survival of organisms on Earth.
We humans are woven into this biodiversity, too.
When just a few strands are lost,
our own well-being is threatened.
Cut too many links, and we risk unraveling it all.
What the future brings is unpredictable,
but biodiversity can give us an insurance policy,
Earth's own safety net to safeguard our survival.



【TED-Ed】為什麼生物多樣性如此重要? (Why is biodiversity so important? - Kim Preshoff)

16181 分類 收藏
稲葉白兎 發佈於 2015 年 6 月 10 日
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