We humans move bad things around, and Nature quickly suffers. But I am not one of those people that believes that everything humans do is bad for Planet Earth. To the contrary, I have researched and written much about the things we do that are essential to restoring and maintaining Nature. We do lots of good work, we should do a lot more, and things would not be altogether better without people. However, humans’ propensity to carelessly move living things great distances is not one of the good things we do. After recently learning about the cause of the disappearance of certain species of local bumblebees, I have been focusing on the pathogens that humans are transporting around the globe.
Plant Pathogens
We don’t have to explore far, or think back very far in history, to see the signs of human mistakes in the kingdom of plants. In the 1990’s, I drove past Waddell Creek on Santa Cruz’s North Coast and gasped when I saw huge patches of tree skeletons – dead and dying Monterey pine trees succumbing from the introduced pine pitch canker disease (Fusarium circinatum – origin Mexico and/or Eastern US). In the last decade, I’ve been similarly shocked at hillsides of brown leaves as forests of tanoaks and live oaks died due to sudden oak death (Phytophthora ramorum – origin East Asia). These are the most recent and widespread results of human carelessness and greed.
Millions upon millions of dead trees are piling up across the world right now due to people vectoring plant disease around the world. Especially with climate change, this is not the right time to be killing trees. Without recalling history, we are doomed to repeat it. We should have learned by now as those recently introduced plant plagues are repeating the devastation of the not-so-distant past. The eastern US lost its dominant forest tree, millions of American chestnuts, to chestnut blight (Cryphonectria parasitica – origin East or Southeast Asia) starting around 1900. A little later, wave after wave of Dutch elm disease (Ophiostoma ulmi 1910 and O. novo-ulmi 1965 – origin Asia) killed millions of elm trees in Europe. No one living recalls the forests of old; soon, no one will recall the beautiful tanoak forests of Central California.
Animal Pathogens
Similarly, human carelessness (and greed) is causing misery and death to many of our wildlife friends. Brucellosis (Brucella ssp. – origin Mediterranean) causes big grazing animals to get sick and sometimes abort their babies. Cattle ranchers worry about the proximity of wild grazing animals that carry the disease. Conservationists are concerned about ranchers wanting to cull wildlife that infect cattle herds. Besides through unregulated hunting, elk, bison, and bighorn sheep populations have probably been depleted through brucellosis and other introduced diseases. This disease also affects humans who become infected through unpasteurized milk or undercooked meat from infected animals.
Another animal disease that humans spread to the detriment of many other species is called chytrid. One type of chytrid (Batrachochytrium dendrobatidis) has caused serious decline and even extinctions in toads and frogs. This disease spread from African clawed frogs imported into the US for the first generation of human pregnancy tests (1930s – 1960s): inject urine into the frog’s skin and it made bumps if you were pregnant – easy, accurate….and a complete disaster for the frogs and toads of the New World. In the late 1980’s, I saw the last of the Golden Toads, a beautiful orange-gold species native to a small patch of cloud forest in Costa Rica. Chytrid found its way into even that remote location, as it found its way into many other seemingly unlikely far-away places, killing off millions of beautiful and sometimes narrowly geographically restricted species. Long-term monitoring plots in Costa Rica and elsewhere in the tropics plummeted in diversity and abundance of frogs. The disease also caused the decline of our local California red-legged frog as well as the frightening annihilation of the Sierran yellow-legged frog, both of which nevertheless survive.
Resistance To … Change or Learning?
My most recent lesson in invasive pathogens was recently with bumblebees. As I engage in restoration and land management across the Central Coast, I recently received notification that the Western bumblebee has disappeared from much of its historic range and now is being seriously considered to be listed as threatened or endangered by the State of California. If you pay attention to environmental media, you no doubt have heard about the effects of pesticides on pollinators. So, hearing about the local extinction of Western bumblebee, you might wonder how pesticides have affected local bumblebees even across the vast areas of parkland and forest where there doesn’t seem to be widespread pesticide application.
While we can’t dismiss the danger of pesticides in affecting pollinators, the more likely culprit for the far-ranging disappearance of this local species of bumblebee is Nosema bombi, a ‘microsporidia’ belongning to group of organisms that might be protozoa or fungi. A bunch of these types of organisms infect humans, but the species infecting, and the effects on, humans is ‘an emerging field.’ Meanwhile, that particular species has been a very serious problem for many bumblebees of the United States. How did it get here? The story again….greed and carelessness: you’d think we should know better by now.
The origin of this bumblebee-killing plague was Europe. Specifically, upstart profit-motivated companies seeking a market in alternative pollinators took our native bumblebees to Europe for breeding, mixed them with diseased European bumblebees, and then brought the disease back to the USA. In the mid-1990s! Companies are applying to do more of this kind of thing right now.
What’s To Be Done?
Each one of us can make a difference to thwart the greed and ignorance at the root of the ongoing introduction of pathogens to the US. I illustrated a very small percentage of instances: there are hundreds or thousands of other examples, even without addressing the pathogens mainly affecting humans (we are all too familiar with recent difficulties of global Covid spread). If even left-leaning media stories included mention of the possibility that pathogen spread has been weaponized for economic warfare, more politicians might be forced to address these issues, which are, after all, national security concerns. National security concerns get bigger pots of federal funding when the voting public gets concerned about them. So, click away at any media story featuring invasive species, introduced pathogens, crop pests, etc: the more literacy we build about these issues, the better. Also…vote for environmentally savvy candidates (if you can find them!). But what do we tell the politicians to do? We tell them to address greed by slowing global trade.
At this point in our knowledge base, we can’t blame ignorance: pathogen introduction is a result of greed. People want money, and they want it now. We have processes in place to detect things we don’t want to come across our borders, but we don’t use them enough to prevent new pathogens from entering. There is no national crisis driving speedy trade in insects, plants, and animals: we can slow down and be more careful. If the politician you support doesn’t understand this, they should. If a politician can’t say that they support a ‘slowing of global trade’ to protect humans and the species that they rely on…that’s a red flag.
-this post originally “printed” in Bruce Bratton’s amazing weekly online blog BrattonOnline.com – check it out!