Plants need four key things to grow: light,
water, carbon dioxide, and fertilizer. Anyone who has a farm, garden, or house plant
knows that plants need the right balance of all of these things. No amount of fertilizer
will help a plant that has no water. Scientists studying the impacts of climate
change on agriculture look at all aspects of the system. Of those four factors, light will change the
least. But water is a big concern. Changing the climate
changes where and when rain falls. Some areas become more wet and other areas become more
dry. Rain might come too early or too late for crops. Hotter air holds more water, so
when it rains, it pours. Floods wash away seeds and plants. Climate change can cause problems for fertilizer
because heavy rain washes it out of the fields and down rivers. A common myth ignores that fact and claims
that “CO2 is a plant food.” This is an oversimplification. It chooses
a single piece of a complicated problem and ignores the other parts. It’s like saying
“humans need calcium so all you need to live on is ice cream”. Carbon dioxide makes plants grow faster when
they are in an ideal environment, like inside a greenhouse, where they have the right amount
of water and fertilizer. But for the basic needs of plants, we need
to consider carbon dioxide AND water. It’s not enough to have the basic necessities
of life. Plants also have to be safe from danger. One big danger for plants is hot temperatures.
Our major agricultural crops have ideal temperature ranges. As the temperature goes up, crop yields
go down. Plants are especially sensitive to extremely hot days. Some other creatures love hot weather. Unfortunately,
many of them are pests like the Colorado potato beetle, the European grapevine moth, and a
nasty wheat blight called FHB or fusarium head blight. Some pests, like FHB, even prefer
the taste of crops that have grown with more CO2 and grow faster. Many pests are migrating
north as the climate warms, into areas where they’ve never been seen before. The overwhelming consensus among agricultural
scientists is that the negative impacts of climate change on crops far outweigh the small
benefit that plants gain from extra CO2.