The Insect Apocalypse Is Coming: Here Are 5 Lessons We Must Learn
By Robert Walker
In a new report, scientists warn of a precipitous drop in the world's insect population. We need to pay close attention, as over time, this could be just as catastrophic to humans as it is to insects. Special attention must be paid to the principal drivers of this insect decline, because while climate change is adding to the problem, food production is a much larger contributor.
The report, released by researchers at the Universities of Sydney and Queensland and the China Academy of Agricultural Sciences, concluded that 40 percent of insect species are now threatened with extinction, and the world's insect biomass is declining at 2.5 percent a year. In 50 years, the current biomass of insects could be cut in half. Such a sharp decline could trigger a "catastrophic collapse of nature's ecosystems."
We have, it appears, a lot to learn to avert the looming insect apocalypse. Here are five critical lessons.
1. Small things tend to get overlooked.
While the volume of scientific research on the threat of species extinction is growing rapidly, most of the focus has been on the declining population of fish and large mammals. Compared to larger species, insect species and their populations get very little attention. In making their report, the authors conducted a comprehensive review and found 73 historical studies of insect decline. That's a tiny fraction of the reports written about the population loss of larger species. Yet arthropods (insects, spiders, crustaceans) account for about half of the world's animal biomass — 17 times more than humans.
2. Small things matter.
When it comes to endangered species, large mammals get all the headlines, but insects are essential to the underlying web of life on which larger creatures depend. About 60 percent of bird species rely upon insects as a primary food source, and birds consume up to 500 million tons of insects every year. Moreover, it is estimated that 80 to 90 percent of wild plants depend upon insects for pollination. And while some insects feed off domesticated crops, other insects help to keep pest populations under control. A 2006 study estimated that insects in the U.S. provided "ecosystem services" worth $57 billion a year. These include pest control, crop pollination and serving as a vital food source for fish and small wildlife.
3. Environmental degradation is accelerating.
Climate change, pollution and the ongoing destruction of forests, wetlands, reefs and other vital habitats are taking an ever-increasing toll on nature. And it's not just insects; environmental degradation is accelerating and rapidly diminishing non-human populations, including birds, fish and large undomesticated mammals. The World Wildlife Fund estimates that wildlife populations, on average, have declined 60 percent since 1970. The International Union for Conservation of Nature now classifies 26,000 species as threatened with extinction, and leading scientists publicly warn that a "sixth mass extinction" has commenced.
4. It’s not just our greenhouse gas emissions …
No one should underestimate the impact that rising greenhouse gas emissions are having on the web of life, but the authors of the insect report indicate that the three largest drivers of insect depopulation are, in order of importance: 1) habitat loss attributable to agriculture and urbanization; 2) pollution, mainly caused by pesticides and fertilizers and; 3) the introduction of invasive species. Climate change, which many believe is the largest driver of ecological ruin, ranked only fourth as a driver of insect decline.
5. … It’s us.
The principal drivers of insect extinction have a common denominator. Simply put, the insect decline, in one form or another (including climate change), is attributable to humans. Our growing numbers and our appetites are driving insects to extinction. There is no letup in sight. World population, presently 7.6 billion, is expected to reach nearly 10 billion by mid-century, and the world's middle class is expected to rise at an even faster rate. Our demand for food, and particularly our appetite for meat products, is leaving less room for other creatures, including insects.
Humans already use a land mass about the size of South America to produce crops for consumption and an area nearly the size of Africa to feed our livestock. Add in the pesticides and fertilizers that we depend upon to boost crop yields, and it's no wonder that insect populations are suffering mightily.
The authors of the report on insect loss warned that, "Unless we change our ways of producing food, insects as a whole will go down the path of extinction in a few decades." Curbing our reliance on pesticides and fertilizers could reduce the loss of insects, but it's our ever-growing need for higher crop yields that has given rise to their use in the first place. Given enough time and capital investments, the farmers of the world might be able to adopt sustainable farming practices without reducing crop yields, but we may not have the luxury of time.
To avoid insect apocalypse, we need to reduce the size of our agricultural footprint. That should begin by preventing runaway population growth and the unsustainable food demand that would go with it. We should increase our support for family planning programs that help to prevent unplanned pregnancies at home and abroad. At present, nearly 40 percent of the pregnancies in the world are unintended. We should also commit to reducing our meat consumption, particularly beef. Meat-based diets require the use of far more land and water and result in much bigger environmental impacts—from greenhouse gas emissions to land degradation—than plant-based diets do.
If insects head toward precipitous decline and extinction, humans can't be far behind. We need to advance our thinking about insects, their importance and what can be done to save them.
Robert Walker is the president of the Population Institute, a Washington-based nonprofit educating the public about the environmental implications of population growth, and advocating for reproductive health and rights.
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By Jacob L. Steenwyk and Antonis Rokas
From the mythical minotaur to the mule, creatures created from merging two or more distinct organisms – hybrids – have played defining roles in human history and culture. However, not all hybrids are as fantastic as the minotaur or as dependable as the mule; in fact, some of them cause human diseases.
When Looking Through a Microscope Isn’t Close Enough.<p>For the last few years, <a href="http://www.rokaslab.org/" target="_blank">our team at Vanderbilt University</a>, <a href="https://www.researchgate.net/lab/Gustavo-Goldman-Lab" target="_blank">Gustavo Goldman's team at São Paulo University in Brazil</a> and many other collaborators around the world have been collecting samples of fungi from patients infected with different species of <em>Aspergillus</em> molds. One of the species we are particularly interested in is <a href="https://doi.org/10.1006/rwgn.2001.0082" target="_blank"><em>Aspergillus nidulans</em>, a relatively common and generally harmless fungus</a>. Clinical laboratories typically identify the species of <em>Aspergillus</em> causing the infection by examining cultures of the fungi under the microscope. The problem with this approach is that very closely related species of <em>Aspergillus</em> tend to look very similar in their broad morphology or physical appearance when viewing them through a microscope.</p><p>Interested in examining the varying abilities of different <em>A. nidulans</em> strains to cause disease, we decided to analyze their total genetic content, or genomes. What we saw came as a total surprise. We had not collected <em>A. nidulans</em> but <em>Aspergillus latus</em>, a close relative of <em>A. nidulans</em> and, as we were to soon find out, <a href="https://doi.org/10.1016/j.cub.2020.04.071" target="_blank">a hybrid species that evolved through the fusion of the genomes</a> of two other <em>Aspergillus</em> species: <em>Aspergillus spinulosporus</em> and an unknown close relative of <em>Aspergillus quadrilineatus</em>. Thus, we realized not only that these patients harbored infections from an entirely different species than we thought they were, but also that this species was the first ever <em>Aspergillus</em> hybrid known to cause human infections.</p>
Several Different Fungal Hybrids Cause Human Disease.<p>Hybrid fungi that can cause infections in humans are well known to occur in several different lineages of single-celled fungi known as yeasts. Notable examples include multiple different species of <a href="https://doi.org/10.1002/yea.3242" target="_blank">yeast hybrids</a> that cause the human diseases <a href="https://rarediseases.info.nih.gov/diseases/6218/cryptococcosis" target="_blank">cryptococcosis</a> and <a href="https://www.cdc.gov/fungal/diseases/candidiasis/index.html" target="_blank">candidiasis</a>. Although pathogenic yeast hybrids are well known, our discovery that the <em>A. latus</em> pathogen is a hybrid is a first for molds that cause disease in humans.</p>
(Left) Candida yeasts live on parts of the human body. Imbalance of microbes on the body can allow these yeasts, some of which are hybrids, to grow and cause infection. (Right) Cryptococcus yeasts, including ones that are hybrids, can cause life-threatening infections in primarily immunocompromised people. Centers for Disease Control and Prevention<p><a href="https://doi.org/10.1371/journal.ppat.1008315" target="_blank">Why certain <em>Aspergillus</em> species are so deadly</a> while others are harmless remains unknown. This may in part be because <a href="https://doi.org/10.1016/j.fbr.2007.02.007" target="_blank">combinations of traits, rather than individual traits</a>, underlie organisms' ability to cause disease. So why then are hybrids frequently associated with human disease? Hybrids inherit genetic material from both parents, which may result in new combinations of traits. This may make them more similar to one parent in some of their characteristics, reflect both parents in others or may differ from both in the rest. It is precisely this mix and match of traits that hybrids have inherited from their parental species that <a href="https://www.nytimes.com/2010/09/14/science/14creatures.html" target="_blank">facilitates their evolutionary success</a>, including their ability to cause disease.</p>
The Evolutionary Origin of an Aspergillus Hybrid.<p>Multiple evolutionary paths can lead to the emergence of hybrids. One path is through mating, just as the horse and donkey mate to create a mule. Another path is through the merging or fusion of genetic material from cells of different species.</p><p>It is this second path that appears to have been taken by our fungus. <em>A. latus</em> appears to have two of almost everything compared to its parental species: twice the genome size, twice the total number of genes and so on. But unlike other hybrids, which are often sterile like the mule, we found that <em>A. latus</em> is capable of reproducing both asexually and sexually.</p><p>But how distinct were the parents of <em>A. latus</em>? By comparing the parts contributed by each parent in the <em>A. latus</em> genome, we estimate that its parents are approximately 93% genetically similar, which is about as related as we humans are with lemurs. In other words, <em>A. latus</em>, an agent of infectious disease, is the fungal equivalent of a human-lemur hybrid.</p>
How A. Latus Differs From its Parents.<p>Elucidating the identity of closely related fungal pathogens and how they differ from each other in infection-relevant characteristics is a key step toward reducing the burden of fungal disease. For example, we found that <em>A. latus</em> was three times more resistant than <em>A. nidulans</em>, the species it was originally identified as using microscopy-based methods, to one of the most common antifungal drugs, <a href="https://www.drugbank.ca/drugs/DB00520" target="_blank">caspofungin</a>. This result provides a clear example of the potential importance of accurate identification of the <em>Aspergillus</em> pathogen causing an infection.</p><p>We also examined how <em>A. latus</em> and <em>A. nidulans</em> interact with cells from our immune system. We found that immune cells were less efficient at combating <em>A. latus</em> compared to <em>A. nidulans</em>, suggesting the hybrid fungus may be trickier for our immune systems to identify and destroy.</p><p>In the midst of the COVID-19 pandemic, our quest to understand <em>Aspergillus</em> pathogens is becoming more urgent. Growing evidence suggests that <a href="https://doi.org/10.1111/myc.13096" target="_blank">a fraction of COVID-19 patients are also infected with <em>Aspergillus</em>.</a> More worrying is that these <a href="https://doi.org/10.3201/eid2607.201603" target="_blank">secondary <em>Aspergillus</em> infections</a> can worsen the clinical outcomes for those infected with the novel coronavirus. That being said, we stress that little is known about <em>Aspergillus</em> infections in COVID-19 patients due to a lack of systematic testing, and none of the infections identified so far appear to have been caused by hybrids.</p><p>So, when it comes to hybrids, some are fantastic (the minotaur), some are helpful (the mule) and some are dangerous (<em>Aspergillus latus</em>). Understanding more about the biology of <em>Aspergillus latus</em> may help in our understanding of how microbial pathogens arise and how to best prevent and combat their infections.</p>
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