Well, I was just reading a fanfic the other day (Quiet, you), a parody piece inspired by the old movie “Night of the Comet,” a film in which most of Earth’s animal life (including humans) is disintegrated radiation by a passing comet. (I don’t know what happened to the sea life, FYI) Now, in the fanfic, the lone surviving heroine is left wondering what effect the lack of fauna is going to have on the world’s planet life (Which had been unaffected), even considering the grim possibility that if the plants died off as well, that she might suffocate on her own CO2.
So, I was left wondering…What WOULD happen to the plants if all the animals died? Apparently, everything above the level of a microbe was affected, including insects. My old copy of “SimEarth” isn’t exactly set up to process this sort of contingency, so I humbly ask my fellow dopers for assistance. To paraphrase Bug Bunny; Is there a botanist in the house?
Well, thanks for your time,
Ranchoth
Many plant species have some sort of symbiotic relationship with animals. The most obvious being those that need an animal (usually an insect) for fertilization and those that make fruits so that their seeds are distributed by animals. These plants are going to be in serious trouble…
But many plants use the wind or water for polination and/or seed distribution and these would do OK.
But, plants consume CO2 and high levels of oxygen are toxic. Its not too much CO2 that the heroine needs to worry about, but too much O2. If there are fungi and microbes still about, they might be able to comlete the carbon cycle and make up for the absence of animals.
OK, so the animal kingdom above unicellular is gone, leaving plants unaffected.
Obviously, any plant species depending on insects or other animals for pollination is in trouble in the long term. (of course the individual plants could still live for a while). On a related note, many species also use animals to distribute seeds (why else would they invent berries?) , and they would suffer a bit.
The other major effect is that there would be no insect or larger animal herbivory. This would dramatically affect which plant species are successful – for instance, milkweeds, mint, briars, and (to some extent) grass would pretty much disappear, as they’re all spending a lot of energy on anti-herbivory devices that would go to waste. They’d be crowded out by soft, tender, but fast-growing species.
I think aquatic ecosystems would be even more dramatically affected than land, as primary consumers make up so much more of the ecosystem. Much more algae-choked ponds and lakes. Not sure how different the oceans would look.
The populations of any plant-eating microbes would just explode. And then all those microbes would evolve like crazy because there wouldn’t be just an eco-niche open, there’d be a gaping eco-grand canyon.
I can see it now: “The Fungus That Walked Like a Cow.”
Make a good B movie title.