Using the Cretaceous impact as an example
Plant effects:
North America - mass extinction & plant kill
Rest of world - Plant kill at event time
"Fern Spike" during recovery
Sea effects:
Crash of planktonic food chain - species dependent on plankton (and those species dependent on the plankton eaters) die off.
Calcium carbonate food chain - shelled (molluscs & the like) suffered heavy losses
Detritus/scavengers - able to survive fairly well
Animal effects:
Largest land animal to survive believed to be approximately the size of a cat.
Largest air-breathing animals to survive (crocs) - are semi-aquatic and can go for multiple months without eating. Young are slow growing and are scavenger feeders for the first few years.
Nuclear winter - complete crash of photosynthesis and food chains derived from photosynthesis
Possible other effects (some theories/possible evidence)
Global firestorm - debris from impact starting meteoric fires worldwide. Secondary effect - buildup of CO2 from fires for greenhouse effect. Will reduce nuclear winter (potentially) but may freeze-bake surviving species and increase extinctions.
Some things to balance out the gloom and doom
Wind patterns (the earth's hemispheres N/S are effectively separate) could have minimize nuclear winter effects in the opposite hemisphere from impact.
RMH
Plant effects:
North America - mass extinction & plant kill
Rest of world - Plant kill at event time
"Fern Spike" during recovery
Sea effects:
Crash of planktonic food chain - species dependent on plankton (and those species dependent on the plankton eaters) die off.
Calcium carbonate food chain - shelled (molluscs & the like) suffered heavy losses
Detritus/scavengers - able to survive fairly well
Animal effects:
Largest land animal to survive believed to be approximately the size of a cat.
Largest air-breathing animals to survive (crocs) - are semi-aquatic and can go for multiple months without eating. Young are slow growing and are scavenger feeders for the first few years.
Nuclear winter - complete crash of photosynthesis and food chains derived from photosynthesis
Possible other effects (some theories/possible evidence)
Global firestorm - debris from impact starting meteoric fires worldwide. Secondary effect - buildup of CO2 from fires for greenhouse effect. Will reduce nuclear winter (potentially) but may freeze-bake surviving species and increase extinctions.
Some things to balance out the gloom and doom
Wind patterns (the earth's hemispheres N/S are effectively separate) could have minimize nuclear winter effects in the opposite hemisphere from impact.
RMH