Hello scientists,
I am reading Rachel Carson's book Silent Spring now. I've read almost half the book today including the chapter on Silent Spring, and as you know Silent Spring was a fundamental book by the marine biologist Rachel Carson which has significantly raised species conservation and the field of ecology to national attention.
She documents precisely how chemicals such as pesticides and herbicides can have devastating effects on an ecosystem via for example having Elm Trees sprayed with DDT for treating Dutch Elm Disease which is a fungal born tree disease carried by a particular species of introduced beetle which distributes the disease to elm trees if it comes into contact with the beetle. Rachel Carson of course documents ways to treat the disease by purging with fire the infected and dead elm trees so that the vector beetles don't return in the spring to find new tree hosts.
But as she describes it in her 1962 book, the most lethal means of trying to solve this problem is spraying the elem trees with DDT to kill the beetle, which is terrible because when the DDT coated leaves fall to the ground they are digested by worms which birds such as the beloved robin ate and dropped dead from DDT exposure. She states that to prove the worms were infected, the worms were fed to a snake at Michigan State University and it died of tremors. Of course, from the title of the chapter, "Silent Spring" the worst affect is the dead quiet silence which results from the birds dying off as the unique sounds of each bird species are no longer heard. The pesticides were not very effective because insect populations are able to recover at incredible rates even when assaulted by insecticides, but their populations can balloon expand if their predators are killed off by eating them which defeats the purpose of using insecticides.
Now, in some conditions like infestations, it's appropriate to use insecticides. But, scientists should definitely study the affect which they have on the food web.
So the question that I have now is what has changed since Rachel Carson wrote her book?
I have read scientific papers which have used logistic regression models from current trends that estimate that we are entering the 6th mass extinction caused by humans. Perhaps the best examples is due to a massive loss of fish species which eat and abide in coral due to global warming which distributes massive quantities of carbon dioxide into the atmosphere which is readily absorbed into the ocean which acidifies the ocean and kills coral on contact because coral is severely pH sensitive. Obviously, a great loss of fish from the ocean equals a great loss of fish eating birds.
Although this is not current news, according to multiple sources and the International Union for the Conservation of Nature (IUCN) Red List, the passenger pigeon used to be the most abundant species of bird in North America abundant enough to block out the sun when flocks flew by, but it was made extinct due to loss of its habitat by human expansion in the 1900s. Now it seems like many cities in the United States do not have much natural beauty eclipsed by skyscrapers and complex traffic ways, so I'm concerned that humans might be driving birds to extinction by means of habitat loss. Also pharmaceutical drugs are heavily regulated by the FDA in the United States, making it very difficult for a drug to make it on the market as it must pass multiple stage trials, and I do believe that it is relatively easy to get a new insecticide or herbicide compound onto the market without doing safety tests. Herbicides especially of phosphates concern me because they are indiscriminate in the plants that they kill as much life on this earth has similar biochemical pathways. I wonder if the death might be due to energy starvation because the phosphate group of the Nucleotide Triphosphates is the main energy currency of cells, so if that's the case that could see those class of chemicals spelling death for any unfortunate grazing animal.
I'm not a bird watcher but I am concerned. Appreciating the beauty of nature still, I feel like I haven't seen much biodiversity of birds. I usually see a robin or a swallow from time to time, I don't usually see any birds with surprising markings. The state bird of my home-state is a goldfinch, but I might as well be hallucinating if I ever claim to see one.
I would love to hear from some ornithologists, or people who study biodiversity, what you think the state of biodiversity is in your country, even if you are not from the United States. (If I have said anything wrong please correct me, too.)
Thank you.
I am not an ornithologist, but I will comment since I do not see others rushing to do so. Rachel Carson died of cancer which she apparently attributed to pollution. Things have not gone as bad as she prophesied (yet, but our new administration may move us closer to disaster). The California condor nearly went extinct because of DDT. Some of the DDT problems included traces on vegetable peels and this came out to the ocean in such places as the Los Angeles outfall. This became concentrated via the marine food web, and become so concentrated in fish that the eggshells were too thin. DDT use has vanished decades and a lot of birds including the California Condor are coming back. Peregrine falcon has also come back pretty well and a good sized population now nests on the sky scrapers in New York. Something that worries me is that about a half century ago a lot of the wetlands along the US West Coast were filled in by land speculators. This continues to stress many migratory water birds.
I spent a number of years working on plant breeding to resist insects, and several good friends are in biological control, all to reduce the need for insecticide use. Dr. Bill Camble at the U of North Carolina has put in decades reducing the tendency of farmers to use more insecticide than they need. Fortunately, most phosphate pesticides are not very long lived in the environment. However, things are far from ideal here. Thank you for your concern,
Definitely, insecticides play a certain role in bird decline. If not directly influencing bird health and fecundity, they have at least to be considered with view to reducing the entomological abundance and diversity. Insects are bird feed... (I am an ornithologist, and of course I know that only a certain range of species depends directly in insects).
Anyway, when it comes to avifaunistic trends, more importantly we have to look at loss of habitat. In intensive agriculture, only few birds have been able to adapt to it. All others disappeared. Coming back to the insects: 'Thanks' to technologies such as roundup-ready, there is not a lot of flora left in a soybean or corn field... No plants (other than crops), no insects, no birds!
Unless we improve in terms of sustainablity and extensivation for more biodiversity, I am afraid we are indeed moving towards the silent spring.
To take some of the pressure away to reduce the need of further intensification, we would have to reduce the growth of human population (or even revert it) and change our nutritional behavior: We eat FAR too much meat, milk products, eggs... A steak a day will keep butterflies from our children away...
Adron,
Please refer to the following publications, both available for download :
NABCI. 2016. The State of North America's Birds 2016.
Partners in Flight Landbird Conservation Plan 2016.
Regards,
Hi Adron, just to extremely summarize a complex question, I can say that in Italy the bird biodiversity is generally increasing since the recent new colonizations (range expansion) or re-colonizations of many species due to protection (among the former: flamingo, cattle-egret, great white heron, cormorant, spoonbill, Ural owl; among the latter: storks, black-winged stilt, and lammergeyer) and the introduction, voluntary or accidental, of exotic species for various reasons (mainly hunting or ex-situ conservation projects). Nowadays, many of them have wild, freely reproductive populations (e.g. sacred ibis, rose-ringed parakeet, northern bobwhite). Other side, there have been a marked decline of population sizes and some local extinctions for some species in the past decades, linked to climate and habitat changes or other factors as shooting and pesticides (shrikes, grouses and vulture in general, Italian sparrow and many passerines of open habitats either in lowland and in highland). Thus, locally, bird biodiversity is diminishing. As usual in Italy, situation is said to be as "leopard spots": some good news and some bad news, which eventually may result in a stable biodiversity
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