The most massive

tsunami perfect storm

is bearing down upon us.

This perfect storm

is mounting a grim reality, increasingly grim reality,

and we are facing that reality

with the full belief

that we can solve our problems with technology,

and that's very understandable.

Now, this perfect storm that we are facing

is the result of our rising population,

rising towards 10 billion people,

land that is turning to desert,

and, of course, climate change.

Now there's no question about it at all:

we will only solve the problem

of replacing fossil fuels with technology.

But fossil fuels, carbon -- coal and gas --

are by no means the only thing

that is causing climate change.

Desertification

is a fancy word for land that is turning to desert,

and this happens only when

we create too much bare ground.

There's no other cause.

And I intend to focus

on most of the world's land that is turning to desert.

But I have for you a very simple message

that offers more hope than you can imagine.

We have environments

where humidity is guaranteed throughout the year.

On those, it is almost impossible

to create vast areas of bare ground.

No matter what you do, nature covers it up so quickly.

And we have environments

where we have months of humidity

followed by months of dryness,

and that is where desertification is occurring.

Fortunately, with space technology now,

we can look at it from space,

and when we do, you can see the proportions fairly well.

Generally, what you see in green

is not desertifying,

and what you see in brown is,

and these are by far the greatest areas of the Earth.

About two thirds, I would guess, of the world is desertifying.

I took this picture in the Tihamah Desert

while 25 millimeters -- that's an inch of rain -- was falling.

Think of it in terms of drums of water,

each containing 200 liters.

Over 1,000 drums of water fell on every hectare

of that land that day.

The next day, the land looked like this.

Where had that water gone?

Some of it ran off as flooding,

but most of the water that soaked into the soil

simply evaporated out again,

exactly as it does in your garden

if you leave the soil uncovered.

Now, because the fate of water and carbon

are tied to soil organic matter,

when we damage soils, you give off carbon.

Carbon goes back to the atmosphere.

Now you're told over and over, repeatedly,

that desertification is only occurring

in arid and semi-arid areas of the world,

and that tall grasslands like this one

in high rainfall are of no consequence.

But if you do not look at grasslands but look down into them,

you find that most of the soil in that grassland

that you've just seen is bare and covered with a crust of algae,

leading to increased runoff and evaporation.

That is the cancer of desertification

that we do not recognize till its terminal form.

Now we know that desertification is caused by livestock,

mostly cattle, sheep and goats,

overgrazing the plants,

leaving the soil bare and giving off methane.

Almost everybody knows this,

from nobel laureates to golf caddies,

or was taught it, as I was.

Now, the environments like you see here,

dusty environments in Africa where I grew up,

and I loved wildlife,

and so I grew up hating livestock

because of the damage they were doing.

And then my university education as an ecologist

reinforced my beliefs.

Well, I have news for you.

We were once just as certain

that the world was flat.

We were wrong then, and we are wrong again.

And I want to invite you now

to come along on my journey of reeducation and discovery.

When I was a young man,

a young biologist in Africa,

I was involved in setting aside marvelous areas

as future national parks.

Now no sooner — this was in the 1950s —

and no sooner did we remove the hunting,

drum-beating people to protect the animals,

than the land began to deteriorate,

as you see in this park that we formed.

Now, no livestock were involved,

but suspecting that we had too many elephants now,

I did the research and I proved we had too many,

and I recommended that we would have to reduce their numbers

and bring them down to a level that the land could sustain.

Now, that was a terrible decision for me to have to make,

and it was political dynamite, frankly.

So our government formed a team of experts

to evaluate my research.

They did. They agreed with me,

and over the following years,

we shot 40,000 elephants to try to stop the damage.

And it got worse, not better.

Loving elephants as I do,

that was the saddest and greatest blunder of my life,

and I will carry that to my grave.

One good thing did come out of it.

It made me absolutely determined

to devote my life to finding solutions.

When I came to the United States, I got a shock,

to find national parks like this one

desertifying as badly as anything in Africa.

And there'd been no livestock on this land

for over 70 years.

And I found that American scientists

had no explanation for this

except that it is arid and natural.

So I then began looking

at all the research plots I could

over the whole of the Western United States

where cattle had been removed

to prove that it would stop desertification,

but I found the opposite,

as we see on this research station,

where this grassland that was green in 1961,

by 2002 had changed to that situation.

And the authors of the position paper on climate change

from which I obtained these pictures

attribute this change to "unknown processes."

Clearly, we have never understood

what is causing desertification,

which has destroyed many civilizations

and now threatens us globally.

We have never understood it.

Take one square meter of soil

and make it bare like this is down here,

and I promise you, you will find it much colder at dawn

and much hotter at midday

than that same piece of ground if it's just covered with litter,

plant litter.

You have changed the microclimate.

Now, by the time you are doing that

and increasing greatly the percentage of bare ground

on more than half the world's land,

you are changing macroclimate.

But we have just simply not understood

why was it beginning to happen 10,000 years ago?

Why has it accelerated lately?

We had no understanding of that.

What we had failed to understand

was that these seasonal humidity environments of the world,

the soil and the vegetation

developed with very large numbers of grazing animals,

and that these grazing animals

developed with ferocious pack-hunting predators.

Now, the main defense against pack-hunting predators

is to get into herds,

and the larger the herd, the safer the individuals.

Now, large herds dung and urinate all over their own food,

and they have to keep moving,

and it was that movement

that prevented the overgrazing of plants,

while the periodic trampling

ensured good cover of the soil,

as we see where a herd has passed.

This picture is a typical seasonal grassland.

It has just come through four months of rain,

and it's now going into eight months of dry season.

And watch the change as it goes into this long dry season.

Now, all of that grass you see aboveground

has to decay biologically

before the next growing season, and if it doesn't,

the grassland and the soil begin to die.

Now, if it does not decay biologically,

it shifts to oxidation, which is a very slow process,

and this smothers and kills grasses,

leading to a shift to woody vegetation

and bare soil, releasing carbon.

To prevent that, we have traditionally used fire.

But fire also leaves the soil bare, releasing carbon,

and worse than that,

burning one hectare of grassland

gives off more, and more damaging, pollutants

than 6,000 cars.

And we are burning in Africa, every single year,

more than one billion hectares of grasslands,

and almost nobody is talking about it.

We justify the burning, as scientists,

because it does remove the dead material

and it allows the plants to grow.

Now, looking at this grassland of ours that has gone dry,

what could we do to keep that healthy?

And bear in mind, I'm talking of most of the world's land now.

Okay? We cannot reduce animal numbers to rest it more

without causing desertification and climate change.

We cannot burn it without causing

desertification and climate change.

What are we going to do?

There is only one option,

I'll repeat to you, only one option

left to climatologists and scientists,