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Yogi Berra, a US baseball player
and philosopher, said,
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"If we don't know where we're going,
we might not get there."
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Accumulating scientific knowledge
is giving us greater insights,
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greater clarity into what our future
might look like in a changing climate
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and what that could mean for our health.
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I'm here to talk about a related aspect,
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on how our emissions of greenhouse gases
from burning of fossil fuels
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is reducing the nutritional
quality of our food.
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We'll start with the food pyramid.
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You all know the food pyramid.
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We all need to eat a balanced diet.
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We need to get proteins,
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we need to get micronutrients,
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we need to get vitamins.
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And so, this is a way
for us to think about
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how to make sure we get
what we need every day
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so we can grow and thrive.
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But we eat not just because we need to,
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we also eat for enjoyment.
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Bread, pasta, pizza --
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there's a whole range of foods
that are culturally important.
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We enjoy eating these.
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And so they're important for our diet,
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but they're also important
for our cultures.
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Carbon dioxide has been increasing since
the start of the Industrial Revolution,
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increasing from about
280 parts per million to over 410 today,
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and it continues to increase.
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The carbon that plants need to grow
comes from this carbon dioxide.
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They bring it into the plant,
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they break it apart
into the carbon itself,
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and they use that to grow.
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They also need nutrients from the soil.
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And so yes, carbon dioxide is plant food.
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And this should be good news,
of rising carbon dioxide concentrations,
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for food security around the world,
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making sure that people
get enough to eat every day.
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About 820 million people in the world
don't get enough to eat every day.
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So there's a fair amount written
about how higher CO2
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is going to help with
our food security problem.
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We need to accelerate our progress
in agricultural productivity
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to feed the nine to 10 billion people
who will be alive in 2050
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and to achieve the Sustainable
Development Goals,
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particularly the Goal Number 2,
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that is on reducing food insecurity,
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increasing nutrition,
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increasing access to the foods
that we need for everyone.
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We know that climate change
is affecting agricultural productivity.
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The earth has warmed
about one degree centigrade
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since preindustrial times.
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That is changing local temperature
and precipitation patterns,
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and that has consequences
for the agricultural productivity
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in many parts of the world.
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And it's not just local changes
in temperature and precipitation,
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it's the extremes.
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Extremes in terms of heat waves,
floods and droughts
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are significantly affecting productivity.
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And that carbon dioxide,
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besides making plants grow,
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has other consequences as well,
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that plants, when they have
higher carbon dioxide,
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increase the synthesis of carbohydrates,
sugars and starches,
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and they decrease the concentrations
of protein and critical nutrients.
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And this is very important for how we
think about food security going forward.
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A couple of nights ago
in the table talks on climate change,
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someone said that they're
a five-sevenths optimist,
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that they're an optimist
five days of the week,
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and this is a topic
for the other two days.
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When we think about micronutrients,
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almost all of them are affected
by higher CO2 concentrations.
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Two in particular are iron and zinc.
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When you don't have enough iron,
you can develop iron deficiency anemia.
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It's associated with fatigue,
shortness of breath
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and some fairly serious
consequences as well.
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When you don't have enough zinc,
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you can have a loss of appetite.
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It is a significant
problem around the world.
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There's about one billion people
who are zinc deficient.
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It's very important
for maternal and child health.
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It affects development.
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The B vitamins are critical
for a whole range of reasons.
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They help convert our food into energy.
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They're important for the functions
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of many of the physiologic
activities in our bodies.
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And when you have
higher carbon in a plant,
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you have less nitrogen,
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and you have less B vitamins.
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And it's not just us.
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Cattle are already being affected,
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because the quality
of their forage is declining.
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In fact, this affects
every consumer of plants.
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And give a thought to, for example,
our pet cats and dogs.
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If you look on the label
of most of the pet and dog food,
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there's a significant amount
of grain in those foods.
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So this affects everyone.
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How do we know that this is a problem?
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We know from field studies,
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and we know from experimental
studies in laboratories.
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In the field studies --
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and I'll focus primarily
on wheat and on rice --
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there's fields, for example, of rice
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that are divided into different plots.
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And the plots are all the same:
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the soil's the same,
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the precipitation's the same --
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everything's the same.
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Except carbon dioxide
is blown over some of the plots.
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And so you can compare
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what it looks like
under today's conditions
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and under carbon dioxide conditions
later in the century.
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I was part of one of the few studies
that have done this.
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We looked at 18 rice lines
in China and in Japan
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and grew them under conditions
that you would expect
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later in the century.
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And when you look at the results,
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the white bar is today's conditions,
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the red bar is conditions
later in the century.
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So protein declines about 10 percent,
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iron about eight percent,
zinc about five percent.
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These don't sound like really big changes,
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but when you start thinking
about the poor in every country
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who primarily eat starch,
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that this will put people
who are on the edge
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over the edge into frank deficiencies,
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creating all kinds of health problems.
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The situation is more significant
for the B vitamins.
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When you look at
vitamin B1 and vitamin B2,
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there's about a 17 percent decline.
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Pantothenic acid, vitamin B5,
is about a 13 percent decline.
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Folate is about a 30 percent decline.
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And these are averages over
the various experiments that were done.
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Folate is critical for child development.
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Pregnant women who don't get enough folate
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are at much higher risk
of having babies with birth defects.
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So these are very serious
potential consequences for our health
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as CO2 continues to rise.
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In another example,
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this is modeling work that was done
by Chris Weyant and his colleagues,
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taking a look at this chain
from higher CO2 to lower iron and zinc --
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and they only looked at iron and zinc --
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to various health outcomes.
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They looked at malaria,
diarrheal disease, pneumonia,
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iron deficiency anemia,
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and looked at what
the consequences could be in 2050.
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And the darker the color in this,
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the larger the consequences.
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So you can see the major impacts
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in Asia and in Africa,
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but also note that in countries
such as the United States
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and countries in Europe,
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the populations also could be affected.
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They estimated about
125 million people could be affected.
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They also modeled what would be
the most effective interventions,
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and their conclusion was
reducing our greenhouse gases,
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getting our greenhouse gas emissions
down by mid-century
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so we don't have to worry so much
about these consequences
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later in the century.
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These experiments, these modeling studies
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did not take climate change
itself into account.
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They just focused on
the carbon dioxide component.
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So when you put the two together,
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it's expected the impact is much larger
than what I've told you.
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I'd love to be able to tell you right now
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how much the food you had for breakfast,
the food you're going to have for lunch,
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has shifted from what
your grandparents ate
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in terms of its nutritional quality.
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But I can't.
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We don't have the research on that.
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I'd love to tell you how much
current food insecurity
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is affected by these changes.
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But I can't.
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We don't have the research
on that, either.
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There's a lot that needs
to be known in this area,
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including what the possible
solutions could be.
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We don't know exactly
what those solutions are,
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but we've got a range of options.
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We've got advancements in technologies.
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We've got plant breeding.
We've got biofortification.
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Soils could make a difference.
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And, of course, it will be
very helpful to know
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how these changes could affect
our future health
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and the health of our children
and the health of our grandchildren.
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And these investments take time.
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It will take time to sort
all of these issues out.
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There is no national entity
or business group
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that is funding this research.
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We need these investments critically
so that we do know where we're going.
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In the meantime, what we can do
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is ensure that all people
have access to a complete diet,
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not just those in the wealthy parts
of the world but everywhere in the world.
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We also individually and collectively need
to reduce our greenhouse gas emissions
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to reduce the challenges
that will come later in the century.
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It's been said that if you think
education is expensive, try ignorance.
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Let's not.
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Let's invest in ourselves,
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in our children
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and in our planet.
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Thank you.
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(Applause)