Ecosystems change long before species are lost

Ecosystems change long before species are lost

Aug. 13, 2013 — Communities in nature are likely to be a lot more sensitive to change than previously thought, according to a new study at Rice University.

---

Share This:

The study, which appears this week in Nature Communications, shows that scientists concerned about human influence on the biosphere need to take a deeper look at how altering the dynamics of a population -- for example, by removing large members of a species through overfishing -- can have measurable consequences, said Rice ecologist Volker Rudolf.

"Natural communities are increasingly altered through human impact, and ecologists have long strived to determine how these changes influence communities," Rudolf said. He noted the disappearance of a species is the most extreme but not the only cause of biodiversity loss.

"That's the last thing that happens after you mess up the entire ecosystem for a long period of time," he said. By then, changes forced upon the structure of a population -- such as the ratio of young to old in a species -- have already been felt up and down the food chain.

Rudolf suspected species play various roles and their effects on the environment change as they progress through their lifecycles, to the degree that altering these life "stages" within a species could have a significant impact. He and Rice graduate student Nick Rasmussen made a considerable effort to prove it.

For the painstaking experiments that started in 2009, Rudolf, Rasmussen and their colleagues chose dragonflies and water-diving beetles to represent species that have major impact on their respective communities -- in this case, fishless ponds -- and then created dozens of miniature environments to analyze that impact. Manipulating the presence of different developmental stages within a predator species in each pond helped the researchers determine that such changes did alter the dynamics of complex ecosystems in a measurable way.

"Other than being the largest and most voracious predators in these communities, they're totally different," Rudolf said of the apex predators. "We figured if we saw any generalities across these two species, then there's something to our theory."

They found that altering which classes of size were present in a population also altered the structure of the entire community and ultimately how the whole ecosystem functioned. Also important, Rudolf said, was that changing the structure of populations sometimes had bigger effects on the ecosystem than changing the predator species.

The results, he said, "challenge classical assumptions and studies that say we can make predictions by assuming that all individuals of a species are the same. You don't expect a toddler to do the same thing as a grownup, and the same is the case for animals."

The study could also explain why such human activities as size-selective harvesting can alter the structure of entire food webs in some ocean systems, even when no species had gone extinct and the total biomass of the targeted fish remained the same, he said.

"While these changes would be hard to predict by the classical approach, our results suggests such changes are expected when human activities alter the population structure of keystone species in an ecosystem," Rudolf said. "Thus, natural ecosystems are likely to be much more fragile then we previously thought."

Welcome to SUV System Ltd!

SUV System Ltd is ISO 90012008 Certified electronics distributor with 10 years of experiences.

We have built up long term business relationship with about many companies which are stockers and authorized agents. we have a steady and reliable supply to meet customer's demands to the greatest extent .Confidently, we are able to lower your cost and support your business with our years of professional service.

SUV System Ltd is Electronic Components Distributor Supplies,Find Quality Electronic Components Supplies Products IC(Integrated Circuits),Connectors,Capacitor,Resistors,Diodes,Transistors,LED at Suvsystem.com. Sourcing Other Energy, Environment, Excess Inventory Products from Manufacturers and Suppliers at Suvsystem.com

Electronic Components distributor:http://www.suvsystem.com

Connectors Distributor:http://www.suvsystem.com/l/Connectors-1.html

IC Distributor:http://www.suvsystem.com/l/IC(Integrated-Circuits)-1.html

LED Distributor:http://www.suvsystem.com/l/LED-1.html

Capacitor Distributor:http://www.suvsystem.com/l/Capacitor-1.html

Transistor Distributor:http://www.suvsystem.com/l/Transistors-1.html

Resistor Distributor:http://www.suvsystem.com/l/Resistors-1.html

Diode Distributor:http://www.suvsystem.com/l/Diodes-1.html

SUV System Ltd insists on the managing faith ofsincereness,speciality,foresight, win-win,so we build up stable-relationship customers located all over the world, including the States, Europe, Argentina, UAE, Malaysia, Australia,and India etc

we are focus on the following fields,and hope we can help you.

Diodes Inc Transistors High Precision Resistors Resistors MURATA IC IR transistor ST Diodes Schottky Diodes LED part NXP Diodes LED Texas Instruments(TI) IC Other Parts NEC Transistors ELPIDA IC Fast Recovery Diodes Diodes Thin Film Resistors AVX Resistors Resistor Networks LINEAR IC MOTOROLA IC IC(Integrated Circuits) Chip Inductors Chip Ferrite Beads ON Transistors SANYO IC Renesas parts IC Thick Film Resistors ON Diodes Switches HARRIS IC Kingbrigt LED PANASONIC Resistors INTERSIL IC Vishay resistors Connectors TDK IC Metal Can Packages Transistors TI IC
http://www.suvsystem.com/a/4883.aspx