- Food chains already under strain before asteroid hit, study shows
- Man's exploitation of resources and reliance on monocrops could place humans in similar danger
By Daily Mail Reporter
|
The mass extinction of dinosaurs by a massive asteroid was made worse because it destroyed the fragile food chain, lessons that modern man should learn, a study warned.
More than 65million years ago a mountain-sized asteroid plunged into the earth in Mexico wiping out many species including the dinosaurs and ending the Cretaceous Period of Earth history.
The study found the food chain was already under strain before the asteroid hit and could not cope with the cataclysm as plant life died off.
Extinction level event: Computer generated simulation shows an asteroid striking the Earth in Mexico's Yucatan peninsula around 150million years ago, the event thought to have lead to the extinction of the dinosaurs
They warned man's exploitation of the earth resources could place humankind in the same peril as we stress the planet with monocrops and drive to extinction animals, plant life and marine species.
Scientists examining the impact zone of the now-buried Chicxulub crater on the coast of Mexico's Yucatan Peninsula said it had wide spreading knock on effects.
Using a computer model they examined what happened up and down the food chain and found the structure of North American ecosystems made the extinction worse than it might have been.
Jonathan Mitchell of Chicago's Committee on Evolutionary Biology said: 'Our study suggests that the severity of the mass extinction in North America was greater because of the ecological structure of communities at the time.'
The team reconstructed terrestrial food webs for 17 Cretaceous ecological communities, seven of these food webs existed within two million years of the Chicxulub impact and 10 came from the preceding 13million years.
The computer model showed how disturbances spread through the food web and developed the simulation to predict how many animal species would become extinct from a plant die-off, a likely consequence of the impact.
'Our analyses show that more species became extinct for a given plant die-off in the youngest communities,' Mr Mitchell said.
'We can trace this difference in response to changes in a number of key ecological groups such as plant-eating dinosaurs like Triceratops and small mammals.'
Feeding time: The team's computer model describes all plausible diets for the animals under study. In one simulation, T-rex only ate Triceratops
The findings suggest a combination of environmental and biological factors meant food webs were already under strain before the asteroid hit, meaning such a large scale disturbance was more likely to have an effect on the survival of species.
Mr Mitchell said: 'Besides shedding light on this ancient extinction, our findings imply that seemingly innocuous changes to ecosystems caused by humans might reduce the ecosystems' abilities to withstand unexpected disturbances,'
The team's computer model describes all plausible diets for the animals under study.
In one run, Tyrannosaurus might eat only Triceratops, while in another it eats only duck-billed dinosaurs, and in a third it might eat a more varied diet.
This stems from the uncertainty regarding exactly what Cretaceous animals ate, but this uncertainty actually worked to the study's benefit.
DINOSAURS 'EVOLVED BIRD-LIKE PLUMAGE FOR COURTSHIP DISPLAYS RATHER THAN FLIGHT'
Bird-like plumage have originally evolved in dinosaurs for courtship displays rather than flight, new findings suggest.
The evidence comes from the first feathered dinosaurs to be discovered in North America.
Researchers in Canada found evidence of feathers in a juvenile and two adult fossils of ornithomimus, a species within the ornithomimid group.
Researchers from the Royal Tyrrell Museum of Palaeontology, and the University of Calgary made the discovery in 75million-year-old rocks in the badlands of southern Alberta.
Ornithomimids were previously thought to have been hairless, fast-running birds, and were depicted as such in the Hollywood dinosaur blockbuster Jurassic Park.
'The discovery, the first to establish the existence of feathers in ornithomimids, suggests that all ostrich-like dinosaurs had feathers,' according to a statement from the Alberta museum.
Fellow researcher Kenneth Angielczyk said: 'Using modern food webs as guides, what we have discovered is that this uncertainty is far less important to understanding ecosystem functioning than is our general knowledge of the diets and the number of different species that would have had a particular diet.'
Data derived from modern food webs helped the simulations account for such phenomena as how specialised animals tend to be, or how body size relates to population size and thus their probability of extinction.
The study looked at how plant deaths affect different food chains and Mr Angielczyk added: 'We aren't trying to say that a given ecosystem was fragile, but instead that a given ecosystem was more or less fragile than another.'
The computer models showed that if the asteroid hit during the 13million years preceding the latest Cretaceous communities, there almost certainly would still have been a mass extinction, but one that likely would have been less severe in North America.
Most likely a combination of changing climate and other environmental factors caused some types of animals to become more or less diverse in the Cretaceous, the researchers concluded.
They suggest that the drying up of a shallow sea that covered part of North America may have been one of the main factors leading to the observed changes in diversity.
The study provides no evidence that the latest Cretaceous communities were on the verge of collapse before the asteroid hit.
Mr Mitchell said: 'The ecosystems collapsed because of the asteroid impact, and nothing in our study suggests that they would not have otherwise continued on successfully.
'Unusual circumstances, such as the after-effects of the asteroid impact, were needed for the vulnerability of the communities to become important.'
The study has implications for modern conservation efforts and Mr Angelczyk said: 'Our study shows that the robustness or fragility of an ecosystem under duress depends very much on both the number of species present, as well as the types of species.'
'What you have is also important. It is therefore critical that conservation efforts pay attention to ecosystem functioning and the roles of species in their communities as we continue to degrade our modern ecosystems.'
The study was published in the Proceedings of the National Academy of Sciences.
No comments:
Post a Comment