ecosystem importance: cicadas' reapearance helps forests (Introduction)

by David Turell , Friday, October 20, 2023, 16:18 (398 days ago) @ David Turell
edited by David Turell, Friday, October 20, 2023, 16:33

Many changes:

https://www.sciencealert.com/cicadas-mysterious-and-dramatic-life-cycle-can-re-wire-ent...

"While the natural phenomenon of the periodical cicada is well known, the impact of this and similar 'biomass pulses' on local ecosystems has never been adequately mapped.

***

"Stuffed to the brim with cicadas, many birds lost their appetite for oak-feeding caterpillars. Plasticine models of the grubs used to gauge predation rates revealed a marked drop in consumption in 2021, with bird strikes declining from around 30 percent to just 10 percent for several months.

"One of the site's most common caterpillar, the grub of the raspberry bud dagger moth (Acronicta increta), showed a marked change in size following the Brood X emergence, with as much as a 50-fold increase in the proportion of large larvae. Presumably, with so many cicadas on offer, the choicest of caterpillars found themselves with a temporary reprieve.

"Moving further down the food chain, a relative rise in oak-feeding herbivores is bound to be bad news for the oak trees. Sure enough, the summer of 2021 saw a spike in damage to the leaves of the immature oaks.

"Just what this might mean in the long term isn't clear. Though prior research on acorn-producing oaks strongly suggests that an increase in herbivores could constrain that season's production of new trees.

***

"'Our study demonstrates that periodical cicada emergences can 'rewire' forest food webs, altering interaction strengths and pathways of energy flow that affect multiple trophic levels," the researchers write in their published report. (my bold)

"Even beyond predation, the deaths of vast numbers of periodical cicadas provide the soil with a pulse of nutrients.

"Meanwhile, as the next brood of cicadas nestle in for a long rest, their burrows loosen and aerate the soil, almost as an apology to the trees above for the brief disruption they'll bring to the ecosystem when they too eventually emerge."

Comment: all tightly organized ecosystems have effects like this. All ecosystems show this knock-on effects even from small changes. It is my conjecture that all ecosystems are interrelated so tightly that changes in one will affect others. And all of this affects the borderline human food supply. Note this opinion:

https://www.sciencemagazinedigital.org/sciencemagazine/library/item/20_october_2023/414...

"Although periodical cicada emergences are short-lived phenomena, lasting for only 5 to 6 weeks, they can initiate a cascade of ecological impacts that propagate up and down the food chain. By providing abundant living prey to predators, carcasses to scavengers and decomposers, and an infusion of nutrients into both terrestrial and aquatic ecosystems, these brief yet intense events initiate a wide range of responses that can last from days to years and can occur immediately or with a considerable time lag. For instance, analyses of long-term data collected by the North American Breeding Bird Survey revealed that populations of some species were abundant only during emergence years and subsequently declined (for example, black- and yellowbilled cuckoos), whereas others were scarce during emergence years but increased substantially the following year, and then stabilized (for example, tufted titmice and gray catbirds). Migratory birds exhibiting cicada-mediated numerical responses can potentially extend the cicadas’ legacy across continents when they travel to distant overwintering sites, affecting recipient communities through “cross-boundary subsidy cascades." (my bold)