Plants don't need animals to survive in terms of nutrients or energy, theoretically they'll do just fine, but without pollinators i wonder for how many generations.
Plants likely could adapt. It’s tough to say when discussing large scale ecosystem changes, especially ones as radical as this. But if we include insects as animals it gets shakey. Plants have evolved to use animals. Certain species of plant emit pheromones or have other means to literally control insects. Some plants like certain corns literally react to the saliva of caterpillars by releasing chemicals that call a species of wasp which lays eggs in caterpillars. Many other species of plant use similar mechanisms for protection, pollination, etc.
There are actually theories that plants influence and control the evolution and even routines of other species through their influence over us via chemicals and other means to encourage or reward behaviors that benefit the plant.
But if animal species were to slowly die off- plants would theoretically do ok. There’s no telling what effect a lack of animals would have on the environment and climate of earth- things like Plankton play vital roles in regulating temperature and atmospheric gas concentrations for example. Many animal species act in ways that regulate the ecosystem and make it suitable for other life. It also depends on what we call “animal.” Many microscopic organisms are “animals” or “micro animals” and many aren’t by strict morphological definitions. If we call anything that is larger than a single cell organism and isn’t a “plant” in that it is incapable of producing its own organic molecules (must get carbon from external sources,) etc- and remember that fungi aren’t plants... it gets muddy.
Most plants don’t move under their own power, and most water plants “go with the flow.” They can’t actively seek carbon sources but the O2 they “breath out” is turned into CO2 by animals so plants can just stay where they are. Without animals- how and if the carbon cycle would work becomes questionable. There’s existing atmospheric carbon, carbon in soil and water. How long would it last, and would plants adapt fast enough to cope with dwindling carbon?
Our best theories say plant life predates proliferation of animal life. Plants have the theoretical ability to survive without animal life assuming there are at least single cell or microscopic organisms. The plants of this world would likely be very different- and to the naked eye they might even be too small to see. But the critical components to the question of their survival are:
-how fast is the extinction of animals?
- how fast can the plants adapt?
- can enough plants in sufficient number and diversity survive to create a sustainable eco system or will things like environmental hazard, disaster and change (fire, flood, drought, etc), disease, or other factors cause their extinction within a period after?
So plants could theoretically do just fine without “animals” if the conditions were right and they were able to adapt.
Funny enough- billions of years ago there were natural nuclear reactors formed in caves. Functional sustained chain reactions. But with humans gone, unmaintained gas lines, industrial processing facilities, power plants and the like would likely explode, meltdown, fail. The radioactive materials could persist in some state for even billions of years in the environment. But many creatures adapt to radiation. Micro organisms can survive intense radiation like that which NASA uses to sterilize space probes. Within less than a single human life time strains of bacteria evolved in NASA facilities that can survive the extreme heat and radiation used for killing all living organisms that could contaminate readings and xeno landscapes.
Fungus (not a plant so technically extinct in our example) has grown in reactor cores like Chernobyl. So conceivably plants, at least moss or mold could also adapt to these conditions. In an extreme scenario the “plants” that survive may not be what we picture- but instead the whole world could be covered in a fine turf of “mold” and look more like a foam ball. These plants might even adapt to process radioactive material for energy. The pants might become radioactive while removing radiation from the environment.
Over many eons, single felled life might begin to evolve once more into more complex forms, suited for survival in this new world. If they prosper and adapt well they may then begin to form into things like simple insects and invertebrates, and more complex life may once again evolve- perhaps even someday another sentient “human level” intelligence. The plants themselves could even possibly form a network that mimics a “brain” and gain consciousness. Who knows? It could end up very much like the world we know today in time- or it could be something we’d never imagine. Life may be elusive, it’s formation a mystery of precise conditions- but once there is life it sure as hell is resilient. The climate and world was very different millions of years ago and species from that age survive today largely the same as they were.
-how fast is the extinction of animals?
- how fast can the plants adapt?
- can enough plants in sufficient number and diversity survive to create a sustainable eco system or will things like environmental hazard, disaster and change (fire, flood, drought, etc), disease, or other factors cause their extinction within a period after?
So plants could theoretically do just fine without “animals” if the conditions were right and they were able to adapt.