杏吧原创

FIRST the bad news. Soaring levels of CO₂ are already contributing
to soaring allergy rates鈥攁nd it鈥檚 going to get much worse.

Allergies have increased from between 2 and 5 per cent of the world鈥檚
population in the 1950s to almost 40 per cent now. And every year the number of
deaths from asthma continues to rise.

The good news is that with a little extra effort, we could improve things a
lot. Starting, appropriately enough, in the greenhouse, here鈥檚 how it works.
When plants in a packed greenhouse use most of the available CO₂, they
stop growing. Old-time growers used to place fresh manure under the benches
which released CO₂ as it decayed and made plants grow faster.

Modern greenhouses, equipped with automatic gas regulators, monitor levels of
CO₂ and release more as needed. Plants grow bigger, mature earlier and
produce more flowers. More flowers means more pollen means鈥攜ou got
it鈥攁llergy city.

Moving outside, male trees and shrubs dominate towns and cities and produce
large amounts of allergenic pollen. City authorities like them because they
don鈥檛 produce messy fruits, seeds and pods to clean up. As CO₂ levels
rise, the trees run amok. Plants grown with increased CO₂ have been
shown to bloom prematurely and produce up to three times as much pollen as
usual. And pollen-bearing trees and shrubs which normally flower only in the
spring now bloom twice a year.

The message is that we have to get serious about CO₂鈥攁nd soon.
Nearer to home, urban planners, landscapers, gardeners, homeowners, all of us,
must stop planting high-allergy trees and shrubs. If we don鈥檛, against a
backdrop of ever-rising CO₂, we will create an allergy epidemic of
truly epic proportions.