Airborne ecologists help balance delicate African ecosystem

Mar 02, 2009
3-D images of African savanna vegetation in areas from which large herbivores have been excluded (left) and allowed access (right) give researchers a detailed picture of the ecological impact of the herbivores. The researchers can quantify not only the amount of vegetation change but also structural changes in the habitat. Image credit: Asner Lab, Carnegie Institution.

The African savanna is world famous for its wildlife, especially the iconic large herbivores such as elephants, zebras, and giraffes. But managing these ecosystems and balancing the interests of the large charismatic mammals with those of other species has been a perpetual challenge for park and game mangers. Now a new study published in the Proceedings of the National Academy of Sciences reports the successful test of new remote-sensing technology to monitor the impact of management decisions on the savannah ecosystem.

"These African savannas are extremely complex," said lead author Gregory Asner of the Carnegie Institution's Department of Global Ecology. "On the ground they are notoriously hard to assess in terms what management decisions, such as controlling fire and large herbivore populations, are doing to the entire ecosystem."

The aircraft-based Carnegie Airborne Observatory (CAO) combines a laser-based 3-D mapping system with high-fidelity imaging spectrometers to create detailed 3-D maps of vegetation over large areas at high resolution (approximately 50 centimeters). For this study, the research team surveyed the vegetation of about 4,000 acres of savanna in Kruger National Park, South Africa. Included in the survey were areas of different soil types and experimental plots where all herbivores larger than a rabbit had been excluded for periods up to 41 years, allowing researchers to discern the effects of both soils and large herbivores on savanna vegetation.

Not surprisingly, the CAO survey found less plant growth and more bare ground in areas where large herbivores had been allowed to graze, compared to areas from which they had been excluded. But the 3-D mapping capability of the CAO revealed differences in the structural complexity of vegetation between herbivore and herbivore-free areas. This has implications for the types of other species these areas are likely to support. And by quickly and precisely quantifying the vegetation differences from the air, the CAO team demonstrated the potential of the new technology as a management tool.

"We are really creating a new way to do ecology," said co-author Shaun Levick. "What we're doing is collecting data for thousands of acres at extremely high 3-D resolution and getting clear answers for the first time as to what different management decisions do in the ecosystem."

Among the surprises in the study's results is that the impact of the large herbivores on vegetation cover is highest in areas where the soil had the highest concentration of nutrients, not areas with poor-quality soil. The researchers interpret this to mean that herbivores concentrate their feeding in areas of high-quality forage, so these areas suffer a disproportionate impact.

The team is preparing a similar study on the effects of fire on savanna vegetation in Kruger Park, according to Asner.

"There have been decades of excellent ground-based research on how different policies regarding fire and wildlife management play out," said Asner. "But the savanna ecosystem is spatially very complicated. With the CAO I think we're getting a picture of the large-scale impact of management decisions. That's what makes this series of studies unique."

Source: Carnegie Institution

Explore further: US top court to review power plant emissions rules

add to favorites email to friend print save as pdf

Related Stories

New laws threaten Brazil's unique ecosystems

Nov 06, 2014

Brazil's globally significant ecosystems could be exposed to mining and dams if proposals currently being debated by the Brazilian Congress go ahead, according to researchers publishing in the journal Science this w ...

What do wildfires have to do with climate change?

Oct 14, 2014

As the western U.S. faces its third year of severe drought, firefighters are still battling two large fires in California. The state, which is experiencing its worst drought since record keeping began in ...

Galapagos invasion is global warning

Sep 03, 2014

A new study led by a PhD researcher at The University of Western Australia has revealed that parts of the iconic Galapagos Islands have been overrun by invasive plants from other parts of the world.

Recommended for you

Tool kit for ocean health

1 hour ago

The ocean is undergoing global changes at a remarkable pace and we must change with it to attain our best possible future ocean, warns the head of The University of Western Australia's Oceans Institute.

Researcher studies interactions between land and water

2 hours ago

Early one morning last January, MIT undergraduate Theresa Oehmke was eating breakfast at the Kilauea Military Camp on Hawaii's Big Island when a colleague burst into the room, yelling, "Oh my god, the plume, ...

Geoengineering our climate is not a 'quick fix'

3 hours ago

The deliberate, large-scale intervention in the Earth's climate system is not a "quick fix" for global warming, according to the findings of the UK's first publicly funded studies on geoengineering.

US to propose stricter smog standard

5 hours ago

Coming full circle on a campaign promise, the Obama administration will propose Wednesday to reduce the amount of smog-forming pollution allowed in the air, which has been linked to asthma, lung damage and ...

Sao Paulo drought issue for global concern

6 hours ago

He cast his rod happily here for 30 years—but where a river once teemed with fish, Brazilian fisherman Ernane da Silva these days stares out over a valley of weeds and bone dry, sun-parched land.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.