Animal Herbivore Species May Mitigate the Effects of Global Warming on Plant Communities

large herbivorExperts in science and ecological studies fear for the current stability and ecological repercussions of plant communities as global warming increases. A study conducted by Eric Post from Penn State university, suggests that the answer to these fears lies in the biological interaction herbivores have with their plant community, as much as it does with the climate change itself.

The study simulated climatic changes and studied the behavioral changes in large plant-eating mammals over a 10-year arctic field experiment. The reason the study was conducted in this environment, is because of the current climatic changes the area is experiencing and because Arctic plant communities are more likely to resist destabilization from climate change. The results suggest that grazing by large herbivores like Caribou, musk ox and others that plant populations are more likely to remain intact when these herbivores exist. The grazing of these animals maintains the plant diversity, even though global warming reduces it.

Plant communities that are not as diverse as others tend to break apart under the warming. The climate-change research of the 1980’s and 1990’s primarily dealt with these less diverse communities. This precursory research focused on the fluctuations of temperature and precipitation on nutrient availability, but didn’t emphasize the indirect effects of the climate change and how interacting species would interact with these communities.

The current study questions the effects of the interaction between species if the planet continues to warm by 1.5 to 3.0 degrees Celsius over the next century. The current study began in a low Arctic plant community in Greenland in 2002. To simulate the 1.5 to 3.0 Celsius increase, Dr. Post erected special warming chambers in fenced off areas. These were built in a cone-shape fashion where the center was hollow. This created a greenhouse effect. Some of these areas were left open to the caribou and musk grazing. Other areas were fenced off to exclude the animals. Thus creating two environments: one where plants and herbivores continue to live normally; the other where animals were not available and the plants were ungrazed.

“The study was meant to study an ecological hypothesis but giving it a new point of view,” suggested Dr. Post. Ecologists have long debated as to the veracity of plant communities being more stable when other species were available. Hence, the combination in the face of global warming. This study asked whether herbivores could contribute towards the stability of a climate-changed environment.

During the 10-year study, both animals and plant communities were carefully observed. Post noted that the grazed and ungrazed environments did present significant differences. The study results confirmed that the caribou and other herbivores acted as a buffer against the degradation of the warming effect on the plant communities. He also noted that shrubs like willow and birch dominated the areas exposed to the warming where the animals were not allowed to graze. The expansion of these shrubs brought shade to neighboring plant, and the buildup of leafs cooled the soil surface and reduced the availability of nutrients in the soil, so other plants could not grow as efficiently. This caused the shrubs to overgrow and prevent other nutritious plants from growing.

However, in areas where caribou and musk ox grazed freely the shrubs were pushed back and other plant diversity thrived. Dr. Posts final conclusions suggests that populations of large herbivores are crucial to the maintenance of plant diversity in a warming climate. Consequently, the factors that threaten the lives of these large herbivores should be analyzed, as these communities are crucial to the maintenance of existing plant diversity.

It is important that conservation associations pay close attention to the preservation of these herbivores in the quickly, changing environment of the Arctic. This will require environmental groups to carefully mediate the interacting stressors with these animals. “These stressors include human exploitation, chemical and mineral interaction and the effects of other predators, as well as the direct effects from the global warming we are currently experiencing,” says Post.

The end results from this study suggest that Arctic plant communities may resist the extreme climatic changes the Arctic is currently undergoing if the population of herbivore species such as caribou, musk ox and other large species remain available.┬áPost’s next project involves the study of plant diversity and its contribution to the stability of carbon dynamics in the soil and atmosphere.

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