Photo: A frog killed by the fungus Batrachochytrium dendrobatidis
Fungal epidemics are spreading to more and more species of animals and plants, threatening humanity with hunger and climate change.
Environmentalists from Imperial College at the University of London (UK) warn of an impending global mushroom epidemic. In an article published in the journal Nature, they cite, for example, the following figures: mushrooms destroy 125 million tons of rice, corn, potatoes and soybeans per year, for a total of $ 60 billion. This could feed 8.5% of the world's population during the same year. Moreover, in this case we are talking only about the damage caused by a constant, "background" infection; large epidemics are not taken into account here - and they may well provoke large-scale famine.
But the main danger is that pathogenic fungi are constantly expanding their specialization, affecting more and more new species. It is easier to see this with the example of animals: in 72% of cases, it is fungi that cause death, leaving bacteria and viruses far behind. Of course, here one cannot but recall Batrachochytrium dendrobatidis from chytridiomycetes, from which tens and hundreds of amphibian species die out all over the world. It is believed that in Central America, this mushroom made about 40% of the species disappear, and so far there are no obstacles to it: neither frogs can develop immunity, nor scientists can create a medicine.
Photo: microbeworld / flickr.com
Another prominent example is white nose syndrome in bats, a fungal disease first reported in 2006 and spreading at an alarming rate. New fungal pathogens, as the authors of the article write, infect species without any distinction, from bees and corals to sea otters.
In some cases, the damage to a person can be calculated directly. For example, bats eat insect pests, and the epidemic of white nose syndrome killing bats is already costing American farmers about $ 3.7 billion a year. But there are other consequences of the mushroom attack: they are difficult to express in monetary terms, but this does not make them less impressive. For example, you can estimate the amount of carbon dioxide that could be processed by trees killed by fungi: this figure is equal to 230-580 megatons, which is 0.07% of atmospheric CO2. Here you need to remember that CO2 is a greenhouse gas, that is, mushrooms can well affect the Earth's climate. They reduce the biodiversity of ecosystems, which is known to make them less stable. But it will not work to brush aside the disappearing ecosystems, since a person, whether he wants it or not,he himself is a part of them. Climate impacts are just the most dramatic example of how we can feel “declining biodiversity”.
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There are several reasons for this success of mushrooms. Firstly, their spores are unusually stable, they can live for a long time outside the host, waiting for years for an opportunity to germinate. Many fungi infect several species at once, and such a wide specialization adds to the mushroom species "vitality". The ability of animals to resist disease also plays in part in favor of fungi, because a resistant individual can carry the disease quite far from the original focus and thus contribute to the spread of the epidemic. Fungi are capable of interspecies gene exchange, which leads to the emergence of new, even more virulent genetic combinations. Finally, their triumphant march is facilitated by human communications, trade and passenger transport.
The researchers advise rallying against the fungal threat as soon as possible, and to begin with, they propose a set of general-purpose measures, from tighter sanitary controls to increased funding for mycological and genetic research. After all, mushrooms can, one terrible day, cause an epidemic among humans that rages among amphibians. I would really not like to be completely defenseless at this moment in front of their onslaught.