《可持续发展的时代》旨在让你了解可持续发展 所面临的关键挑战和实践途径 即兼顾社会包容性和环境可持续性的经济发展
What is Biodiversity?
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來自 Columbia University 的課程
可持续发展的时代
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從本節課中
Saving Biodiversity
Professor Sachs reviews the various threats to the world's ecosystem and biodiversity.
與講師見面
Jeffrey Sachs
Director, Earth Institute; Quetelet Professor of Sustainable Development; Professor of Health Policy and Management
[MUSIC]
We've been examining what happens, when a
growing world economy collides against planetary boundaries.
We have a world output now, of 80 to $90 trillion, 7.2 billion people.
We know that the numbers are continuing to rise.
We know that the world economy is continuing to grow at three
to 4% per year, meaning a doubling, every 20 years or so.
We know, that there are already huge pressures on
the world's ecosystems, on the climate, on the oceans.
And we have not yet found a way of
course, to reconcile that continuing growth, with environmental sustainability.
We've studied a few ways that this, collision or this trespass
of planetary boundaries is occurring, climate change being the most dramatic.
Pollution of the air and water and the dangers to our cities being another.
I want to go into greater depth now, on the question
of the viability of other species, the biodiversity on the planet.
I've mentioned several times, that humanity
is putting so much pressure on the
Earth, that we're actually causing a dramatic
increase in the rate of species extinction.
Maybe 100 to a 1000 times, greater rate of
species extinction, than was occurring before the the industrial revolution.
That loss of species and many other phenomena
associated with it, such as the decline of genetic diversity within species.
The decline of abundance of species, even when they're not
being pushed to extinction, but just to smaller and smaller numbers.
That combined effect is so large, that it is
causing what could be the sixth great extinction on the planet, as I've
discussed, and it is causing huge threats to humanity.
As always, whether it's with climate change, or dangers to our cities,
or challenges of health and education,
first we need to understand, what's happening?
Why is it happening?
What are the mechanisms?
We have to do a differential diagnosis of the losses
to biodiversity, and to the rising rates of species extinction.
Then we have to analyze, what we can do
about it, what's the prescription, what are the possible approaches?
Now, there's one overriding truth to this sixth
wave of extinctions and to the threats to biodiversity.
And that is, that the threats are coming from many,
many different angles, as is true in almost everything we're studying.
We're dealing with a complex system, where there's not a linear effect from
a single cause to a single outcome, and then onto another effect.
There are multiple stressors, multiple drivers of environmental change, multiple
causes of species extinction or decline of abundance and genetic diversity.
We need to understand the complexity of this system because no single approach
is going to be sufficient to [COUGH] reversing the trends that are underway.
Heading off this sixth great extinction that is a threat,
to not only millions of other species, but to one that we also have a
especially strong vested interest in, and that's Homo sapiens, that's us.
And so we need to get into the very complex nature of this threat.
You're looking at an example of biodiversity, the incredible diversity
of species and interactions in this marine environment that you're viewing right now.
And of course, what you see are multiple species of animals and plant life.
Many species are microscopic, and you don't see them.
You see the interactions of the fish,
corals, and we know the microscopic plankton
for example in the oceans, with the non-living part of
the system in front of you, the fluxes of energy, of sunlight
of nutrients that are arriving in this
ecosystem from a variety of sources.
What is an ecosystem?
It is exactly that collection, of plants and animals and
microbial life, interacting with the abiotic or
nonliving part of the local system, with the energy and nutrient fluxes.
The key is that this is a set
of living organisms together with the non-living environment.
Interacting in a system and of course, what ecologists do
in studying ecosystems, is study the fluxes and dynamics of the system.
How does nutrient flow take place within a
food web and within the processes of metabolism.
Of, oxidation, respiration, [COUGH] and, photosynthesis, and other basic
processes of, the metabolism of the living organisms, within the system.
How does the diversity of the, species and the diversity of the individual
organisms within a species, affect the behavior of that whole ecosystem?
So when we have an ecosystem, we're also interested in another core concept.
And that is the biological diversity or biodiversity of that ecosystem.
And of the biodiversity across ecosystems, as
ecosystems, marine, and terrestrial, interact with each other, to produce
outcomes, at an even higher level, of aggregation and organization.
So what is bio-diversity?
Bio-diversity is the variability of life, and it
is variability that occurs at all different levels of organization.
We care about the variability of life within a
species, each of us is different from from other people.
We have different genetic codes.
We carry different effects of our [COUGH] our environment.
We know that the relationship of
environment and genetics, is extremely complicated.
We found out that it's even more complicated than we thought, through the
emerging field of epi-genetics, which tells us that the environment affects, how
our genes code or don't code, in ways that actually can transmit across generations.
Even not in the DNA itself, but in the way that that DNA
is expressed in cells from a parental generation to offspring.
So, we care about the variation, within a species.
We care about the interaction across species.
All of the various relationships of predator and prey, and mutualism,
and parasitism, and the ways that species interact, and and
live together and are part of, larger food chains and nutrient fluxes.
And a part of the way that, the disease is pathogens, transmit within an ecosystem.
And we care about the biological diversity across ecosystems.
Because the interaction of ecosystems, of dry land ecosystems,
or desert ecosystems, interacting with
the humid ecosystems, with alpine or marine
ecosystems, is also absolutely crucial for understanding, how
any of those individual ecosystems functions, but also understanding
the global functioning of the, the earth as a whole.
What happens in the oceans or what happens in the polar
regions or what happens in the rain forests, affects global dynamics
of heat dissipation, of the water cycle, and through
multiple processes, affects ecosystems all over the world.
So there are distant relationships between
changes in the pole-ward regions, for example.
And what happens even in the tropics or, or
places that are thousands and thousands of kilometers, distant.
So, biological diversity or biodiversity, requires us to
understand the variation of life, at all different levels
of organization, and to understand how that
variability affects the performance of ecosystems, in ways that matter.
One of the most important studies that was done,
in recent decades in fact, on the functioning of
ecosystems, was a major global effort [COUGH] which reported
in the year 2005, called the Millennium Ecosystem Assessment.
It took a global view of the major ecosystems in the world,
and tried to give a conceptual framing, of how they're
functioning, how they're interacting and what they mean for humanity.
And one of the important schematic ideas that came out of the
millennium ecosystem assessment is, this chart, that you're looking at right now.
The idea of this chart is to define, how ecosystems affect human well-being.
That's not the only thing we care
about ecosystems, but it's a pretty important part.
And you see on the left,
various categories of ecosystem services, so-called.
Ecosystem services are the benefits, that ecosystems give to
humanity, and to other species, I would like to add.
And those benefits come in a variety of forms.
Partly, ecosystems directly provide for human needs.
Provisioning services, growing food, providing fresh water.
providing, wood and fiber for building structures, for our clothing.
Providing biomass for our fuels.
So, provisioning is one direct and obvious category.
A bit less, direct, but
absolutely profound, is the idea of regulatory ecosystem services.
Ecosystems control basic climate patterns, disease patterns
cycling of crucial nutrients, in ways that are of fundamental importance to humanity.
Even if they're not directly the provisions
of things, that we eat or directly consume.
So for example, ecosystems in their
functioning, have huge effects on climate regulation.
If, the pole-ward
Nordic and Arctic ecosystems are
heavily changed by climate warming, then we're also going to
get powerful feedbacks that could be o, of tremendous adverse consequence.
For example, the melting of the great ice sheets.
Or the decline of ice covering the seas, changing the reflectance of the
planet and providing a massive feedback,
amplifying climate change, coming from greenhouse gasses.
Or, the melting of ice in the Tundra, releasing massive
amounts potentially, of methane or carbon dioxide, in a feedback mechanism.
So, ecosystems provide regulatory services, either helping
to sustain a climate in a safe zone, or if
these ecosystems get perturbed, amplifying adverse changes that are
coming from other factors, such as greenhouse gas concentrations.
Flood regulation is the second kind of ecosystem service.
Coastal areas are often protected by the mangrove swamps
just off the coast or by other topographical features of
ecosystems, and if those get perturbed, if those are
lost by human-induced changes, that can lead to great dangers.
The coastal areas around New Orleans, for example,
were degraded by the ways that human activity led
to changes of the dynamics of the Mississippi
River, as it flows into the Gulf of Mexico.
And the loss of those coastal barriers meant,
that when Hurricane Katrina slammed the Gulf of
Mexico, this added tremendous force and damage, to
New Orleans and to the rest of the coastline.
And so, the loss of coastal regulatory
protection because of human activity, clearing mangrove
swamps or changing river flow dynamics, had
a hugely consequential and adverse effect for humanity.
Ecosystems regulate disease and pests, and when ecosystems are degraded, pests
or invasive species,that is species that have been brought in by accident or even
inadvertently, from outside a particular place
and maybe don't have natural predators within
that new environment, can spread, can take over, can be essentially like wild
weeds or spreading parasites, with devastating consequences to
food production, for example, or to human health.
The ecosystems for instance, the wetlands which are a major part of the water cycle
help to provide fresh water help to replenish ground water.
Vital for household use or for crop production.
When ecosystems are deranged, we can lose water services
needed to grow food and needed for human health.
Ecosystems have a third category called
supportive ecosystem services [COUGH] you see here.
Nutrient cycling or the way that soils are
formed, through the interaction of biotic and abiotic processes.
And soil formation then, is a crucial
underpinning of course, of our agricultural productivity.
And finally, the millennium ecosystem assessment identified
cultural features, which are our values, our aesthetics.
One of the, greatest scientists, of our age,
E.O. Wilson, the great biologist at Harvard University, one of
the leaders in understanding biodiversity and one of the
leaders in understanding human nature, in, in our world,
has given the idea that, humanity has a deeply ingrained love of bio-diversity.
That we even inherited as part of
our, our, our mental baggage during human evolution.
A trait that he calls biofelia or love of of a
diverse of a biology and the, the bioda, and our biodiversity.
And Professor Wilson has given extensive
compelling evidence from the range of anthropological
studies for example, of how humanity feels at home, in certain natural environments.
And how the degradation or derangement of
those natural environments can deeply upset our
cultures, our mental well being our sense
of aesthetics, our overall quality of life.
Well, those ecosystem services, translate into
many dimensions of human well-being, our physical
security, the materials that we need for
life, our human, physical and mental health.
Our ability to interact fruitfully in society, in other words,
there are contributors to our social capital, and to the preservation
of social relations and as the millennium ecosystem assessment emphasized,
they contribute to our freedom, our capability to accomplish our life's tasks.
So, ecosystem services are central, they are a threat
because they are such core, dimensions to
our human well being, we now have to turn to the question of,
how biodiversity contributes to the functioning of
ecosystems, and what happens when biodiversity is put at
great threat, by human activity.
That's our next subject.
