1 . The Arctic's permafrost is inciting— and fast. That's bad news, because these frozen soils store billions of tons of carbon, just waiting to be released. So is there a way to save the permafrost? One team of researchers thinks it may have found a possible solution: big animals, herbivores - animals that eat only plants.
Back in 1996 researchers started an experiment called Pleistocene Park. They fenced in about eight square miles of land in northeast Siberia. Then they introduced different types of herbivores: reindeer, horses, bison, sheep and other large creatures.
Since then, scientists have studied these animals' effects on the ecosystem. One outcome is that these large herbivores help keep the ground very cold — cooler than it would otherwise be.
“The snow in winter is important for soil temperature, because it acts as an insulating layer. So the air in winter, at the high latitudes, is much colder than the soil." Philipp Porada, a vegetation ecologist at the University of Hamburg. "So the idea of this experiment was to introduce large herbivores — and to quantify their effects on soil temperature to see if they can actually protect permafrost soils against melting. And this works because of the animals' trampling (践踏), and this leads to less insulation of the soil against cold air temperatures and results in a cooling effect.”
Freezing air reaches the soil more easily. Porada and his colleagues realized the significance of this effect, so they pulled data from Pleistocene Park and Sweden to model what effect herbivores could have on permafrost if they lived in large numbers in the Arctic.
They found that even in a worst-case situation, some four degrees Celsius of global wanning: “These herbivores in the model reduce soil temperature substantially, by 1.7 degrees on average. And this leads to a preservation of around 80 percent of the original — today's permafrost area. Without the herbivore effect in the model, only 50 percent of the permafrost area would remain by the year 2100. So we can say the effect of the herbivores in the model leads to a substantial preservation of permafrost soil."
1. Why is the Pleistocene Park Experiment mentioned?| A．To provide the past research data. |
| B．To share soil preservation experience. |
| C．To introduce a way to save permafrost. |
| D．To prove animals' effect on soil temperature. |
| A．Covering. | B．Blocking. |
| C．Storing. | D．Freezing. |
| A．Cooling the ground. | B．Heating the soil |
| C．Damaging the ground. | D．Softening the soil. |
| A．Permafrost Is Disappearing | B．Preservation of Permafrost |
| C．An Experiment on Herbivores | D．Herbivores Help Save Permafrost |
