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In 1845, Ireland's vast potato fields
were struck by an invasive fungal disease

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that rapidly infested this staple crop.

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The effect was devestating.

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One million people died of famine,

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and over a million more were forced
to leave Ireland.

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Nowadays, we avoid such agricultural
catastrophes with the help of pesticides.

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Those are a range of manmade chemicals
that control insects,

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unwanted weeds,

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funguses,

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rodents,

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and bacteria


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that may threaten our food supply.

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They've become an essential part
of our food system.

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As populations have grown,
monoculture, single crop farming,

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has helped us feed people efficiently.

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But it's also left our food
vulnerable to extensive attack by pests.

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In turn, we've become more dependent
on pesticides.

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Today, we annually shower over 5 billion
pounds of pesticides across the Earth

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to control these unwanted visitors.

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The battle against pests,
especially insects,

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has marked agriculture's long history.

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Records from thousands of years ago

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suggest that humans actively burned
some of their crops after harvest

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to rid them of pests.

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There's even evidence from ancient times
that we recruited other insects to help.

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In 300 A.D., Chinese farmers specially
bred ferocious predatory ants

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in orange orchards
to protect the trees from other bugs.

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Later, as large-scale farming spread,

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we began sprinkling arsenic, lead,
and copper treatments on crops.

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But these were incredibly toxic
to humans as well.

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As our demand for more, 
safer produce increased,

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so did the need for effective chemicals

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that could control pests
on a grander scale.

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This ushered in the era 
of chemical pesticides.

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In 1948, a Swiss chemist named
Paul Hermann Müller

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was awarded a Nobel Prize 
for his discovery

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of dichlorodiphenyltrichloroethane,
also known as DDT.

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This new molecule had unparalleled power
to control many insect species

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until the 1950s,
when insects became resistant to it.

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Worse, the chemical actually drove
dramatic declines in bird populations,

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poisoned water sources,

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and was eventually found to cause
long-term health problems in humans.

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By 1972, DDT had been banned
in the United States,

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and yet traces still linger
in the environment today.

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Since then, chemists have been searching
for alternatives.

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With each new wave of inventions,
they've encountered the same obstacle -

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rapid species evolution.

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As pesticides destroy pest populations,

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they leave behind 
only the most resistant individuals.

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They then pass on their 
pesticide-resisting genes

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to the next generation.

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That's lead to the rise of super bugs,

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such as the Colorado potato beetle,

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which is resistant to over 
50 different insecticides.

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Another downside is that other bugs
get caught in the crossfire.

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Some of these are helpful predators
of plant pests or vital pollinators,

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so erasing them from agriculture
wipes out their benefits, too.

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Pesticides have improved over time

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and are currently regulated by strict
safety standards,

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but they still have the potential
to pollute soil and water,

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impact wildlife,

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and even harm us.

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So considering all these risks,
why do we continue using pesticides?

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Although they're imperfect,

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they currently may be our best bet
against major agricultural disasters,

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not to mention mosquito-born diseases.

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Today, scientists are on a quest for
alternative pest control strategies

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that balance the demands
of food production

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with environmental concerns.

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Nature has become a major source
of inspiration,

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from natural plant and fungal chemicals
that can repel or attract insects,

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to recruiting other insects 
as crop bodyguards.

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We're also turning to high-tech solutions,
like drones.

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Programmed to fly over crops,

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these machines can use 
their sensors and GPS

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to carry out more targeted sprays

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that limit a pesticide's wider 
environmental impact.

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With a combination 
of biological understanding,

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environmental awareness,

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and improved technologies,

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we have a better chance of finding
a holistic solution to pests.

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Chemical pesticides may never shake
their controversial reputation,

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but with their help,

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we can ensure that 
agricultural catastrophes

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stay firmly in our past.