Mess with Mother Nature and You May Be Sorry

Until I visited the Tucson Botanical Gardens I had not realized how many climates around the globe are similar to that of the Sonoran Desert. In the Cactus and Succulent Garden, planting areas are devoted to plants from hot, arid climates on six continents. Only Antarctica is missing from the line up.

These climatic similarities encouraged importation of species from other continents, other ecosystems, to the cities and towns of southern Arizona. The earliest importers were probably Franciscan monks who brought olive trees to southern California in 1769. The planting of olive trees soon spread to Arizona, and today one often sees olive trees in Tucson yards, where the fruit may be seen littering the ground, rotting away.

This seems a terrible waste of a valuable resource to me. I wish I could organize an urban hunter-gatherer group to harvest olives as well as the fallen citrus fruit I see in neighborhoods all around the city.

Sadly, Pima County outlawed the planting of olive trees in 1984, so all of the olive trees one sees here are at least 32 years old. Planting new olive trees was banned because olives’ pollen is a powerful allergen for some people, which rather spoiled the reputation of southern Arizona as a haven for allergy sufferers.

Later, the Department of Agriculture, particularly its Extension Service, was an avid and enthusiastic, if ill-informed, promoter of various non-native species all over the country. One in particular, the African sumac, was touted as a leafy, shade-giving tree for Arizona, and was widely adopted for that reason. Unfortunately, the female African sumac also is a manic seed-producer. Also, its roots spread extensively, crowding out native species. Many people are allergic to its pollen, as well, and the tree is now considered an invasive species. In our yard alone there are six African sumac trees, at least two of which are female. This one is right outside our front door, loaded with yellow blooms whose pollen has had me sneezing and hacking for two weeks now.

Personally I’d prefer six olive trees. Even if they made me sneeze they would also compensate by producing delicious fruit.

We humans have made many irremediable transplants from one ecosystem to another. Pythons from Burma, sericea lespedeza from Japan, Flying silver carp from Asia, and others have taken hold in the United States, wrecking highly evolved ecosystems from the Florida Everglades to the plains of Kansas to the Great Lakes and even the deserts of the Southwest.

Copyright 2016 by Shirley Domer