Prevention doesn’t come naturally to the human spirit. Even if we know better, paying the immediate cost often seems more daunting than the possibility of paying a much higher cost (death, say) at some unknown date in the future. This emotional disconnect is what makes it so hard to persuade people to eat less, exercise more, practice safe sex, or take action to prevent climate change.
Lately, the “why worry?” line of thinking has turned up in the debate over invasive species. If you think it’s hard making parents understand that their unvaccinated child could die from measles, just imagine how hard it is to convince them that they should also worry about, say, invasive beetles turning up in the backyard. To make prevention even less likely, some critics now argue that introduced species are often harmless, or in some cases beneficial, and that there are just too many of them to fight. At best, they say, we spend a great deal of money to slow down the invasion. But we can never stop it completely.
A new case study being published in the journal Frontiers in Ecology replies—if I may sum up the scholarship in a phrase—that this is a lot of crap. The coauthors look at the current poster child of invasive species, the emerald ash borer, a beetle with a glittering green carapace and a nasty habit of killing some of the most majestic trees lining the streets of North American cities, as well as in our yards and forests.
Emerald ash borers (also known as EAB) arrived from Asia by accident in the 1990s, and biologists first detected them in Detroit in 2002. In North America, they focus exclusively on ash trees (hence the name), and as their larvae bore into a tree, they block off its ability to transport nutrients and water.
Alarmed at the prospect of dying forests, the Nature Conservancy and the National Center for Ecological Analysis and Synthesis launched a wide-ranging series of studies on the problem. “By 2003, at least 5–7 million ash trees were dead or dying in a six-county area of southeastern Michigan,” the authors of one such study wrote early this year, “and it was becoming apparent that EAB had the potential to devastate ash on a continental scale.”
The new study looks at the preventive measure undertaken by 70 signatory countries, including the United States, to slow or stop the invasion. ISPM15, as it’s known, requires manufacturers in international trade to treat wood pallets and wood crating (like the box holding your supermarket clementines). Treatment typically involves heat or fumigation with an insecticide, at a cost of about $1.50 per pallet. That added up to a whopping $437 million in 2005, the first year of implementation, with the expectation of continuing costs at a much lower level as pallets run through their typical six-year life span.
So was it a waste of money? McGill University biologist Brian Leung and his coauthors calculated how many insect pests turned up on crates and pallets before ISPM15. They noted that the required treatments are 52 percent effective, meaning that they don’t kill every insect—they just slow down the invasion. But they also noted that the treatment doesn’t just target emerald ash borers.
With no treatment at all, says Leung, the United States could have expected 200 other wood-boring insect species to become established here. This country can still expect “substantial increases in forest pests,” according to the study, at least in part because we consume so many imports. But ISPM15 at least cuts this army down to an ultimate invasive force of 100 species. Making the treatment 100 percent effective would require more expensive technologies or switching to plastic, says Leung, and might well be worth it. That’s a cost-benefit analysis he and his coauthors have not yet undertaken.
So looking just at the ISPM15 rules as they stand, here’s the bottom line: The United States will begin to see a return on investment in 2016. Counting all the costs of treatment, as well as all the avoided costs from damage to our forests and street trees by invasive insect pests, we will enjoy a net benefit in excess of $11 billion by mid-century. In other words, prevention works, even if the “substantial net benefits…become apparent only after multiple decades.” (In an interesting parenthetical afterthought, the coauthors add that the same holds true for policy to reduce carbon emissions.)
All these numbers may still seem abstract. So let’s make it personal: Last year, after my father’s death, I was getting ready to sell his house. One day in the front yard, I looked up at three tall, magnificent trees that had been growing there my entire life. It was June, and they were suddenly bare. “Emerald ash borers,” the tree contractor explained. The bill to remove the trees was $2,900.
Step out into your own yard, and you may see the same thing, if you are lucky enough to have ash trees. It might make you think differently next time biologists warn that we need to act now to keep something bad from happening in the uncertain future. You may even find yourself thinking, like me, that paying $1.50 today is much less painful than paying $2,900 down the line.