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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.
We need to get vitamins.

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And so this is way for us
to think about how to make sure

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we get what we need every day

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so we can grow and thrive.

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So 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

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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,
they break it apart

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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 pre-industrial 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-seventh 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 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 is the same,
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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and 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 Wyant