A study, presenting a 5000-year environmental history of the popular tourist destination, Amboseli National Park in Kenya, has shown that the impact of climate change on land is more rapid than previously thought.

Environmental changes surrounding the savannah and wetlands occur within decades [Credit: University of York]

Over the period, environmental changes surrounding the savannah and wetlands occur within decades, revealing a dynamic eco-system that is constantly evolving and responding to climate change.

The study suggests that further considerations over how strictly National Park boundaries are managed are needed in order to keep pace with the changing environment.

The team found that the most significant changes occurred over the last 500 years, which were associated with the arrival of Massai people and the ongoing ivory trade.

Sediment analysis showed that the Massai people used fire to help cultivate and control the landscape, which altered the vegetation composition and woodland ecosystem over a short space of time.

Esther Githumbi, from the University's Environment Department, said: "East African savannahs support large human and animal populations, but are undergoing rapid developments and pressures on water resources.

"Changes are leading to reductions in wildlife habitats and biodiversity loss, so it is important to understand how various environmental factors have interacted in the past, particularly human influences, to get a realistic idea of what the future might look like."

Analysis shows that sparse woodlands and shrubs characterised the landscape 5000 years-ago, and the expansion of wetlands over the years demonstrated the high variability in vegetation as a response to atmospheric climate change. Vegetation changed still further depending on the varying size of the herbivore animal population.

Professor Robert Marchant, co-author from the University's Environment Department, said: "You have to see all of these different climate, animal, and human interactions in one dataset in order to get a realistic sense of how each impacts on the other. By far the biggest impact to the landscape, both in the past and today, is human activity."

Research demonstrates that with the arrival of humans to the area, portions of wetlands, crucial to the survival of a diverse animal population, were turned into agricultural production, utilising lands that would have been previously unsuitable for sustaining human life.

Today, the Maasai people do not use fires to open the landscape for settlement or control pests affecting their livestock, because the habitats are now suitable for them live and work, as well as being illegal to this part of Africa.

Esther said: "Now that we know how rapidly these changes occurred in the history of this area we can better predict the future. Our project is just one of many around the world looking at land-based climate changes.

"Once we have full datasets from these countries, the aim is to combine the results to get a global picture of what is happening on land. For the savannahs of East Africa this could mean considering how decisions are made about boundary lines around protected lands, given that the ecosystems can change more quickly than previously thought."

The research is published by the Royal Swedish Academy of Sciences.

Source: University of York [February 08, 2018]

In the peaceful grasslands of northern Tanzania, a frenzy of research is occurring. The Olduvai area (from the Maasai name "Oldupai," for a native succulent plant) came to fame through the findings of Kenyan archaeologists and paleoanthropologists, Louis and Mary Leakey. Their research, beginning in the 1950s, uncovered numerous fossil hominins (the tribe of great apes, including modern humans) and stone tools dating back as far as two million years and earned the area the nickname "cradle of humankind." Olduvai has since become a hub for those exploring the origins, and future, of humanity.

Local Maasai staff lay out the geophones, a crucial piece of equipment in seismic imaging  of the Olduvai Basin [Credit: 2017 Sherif Hanafy]

Paleoanthropologists, however, no longer have sole claim here. A full picture of human evolution cannot be gleaned from fossils alone, but relies on understanding their environmental context.

To this end, a team of KAUST's geophysicists are conducting crucial surveys of the site's geology. Using state-of-the-art techniques developed for oil exploration, Gerard Schuster, Sherif Hanafy and doctoral student Kai Lu, with scientists from Indiana University, USA, and Liverpool University, UK, are mapping the shape and structure of the Olduvai Basin's bedrock.

This is no mean feat because the basin is six kilometers wide and almost half a kilometer deep. It comprises a complex mixture of sedimentary and volcanic rocks, traversed by multiple geological faults. Lying at the heart of the East African Rift Zone, where the tectonic plates making up the Earth's crust are moving apart, Schuster explains that the basin, "evolved and deepened over time as the ancient lake above it expanded, contracted and shifted laterally in space, partly caused by a sequence of eruptions of neighboring volcanoes."

Rewriting history

Two complementary experimental approaches are used: boring wells to extract physical 'cores' of sediment laid down over millions of years and the KAUST team's seismic imaging studies. Together, they are rewriting the geological history of Olduvai.

The seismic experiments are based on a remarkably simple premise: a heavy weight is repeatedly slammed onto the ground, creating vibrations that travel through it until they are reflected or refracted (bent) as they move from one material to another (in the same way that light reflects off a mirror or bends as it enters water). A series of receivers (known as geophones) are placed just below the ground to monitor these reflected and refracted waves. By recording the time taken for the waves to reach each of the geophones, the team can calculate the speed at which they traveled. In a similar way to ultrasound scanning, these measurements are built into a picture of the subsurface geology, including the basin's shape and size, and the location of buried faultlines.

Complex and logistically challenging, the method is intriguing to local people, many of whom are employed on the project. As Hanafy explains, "they are used to working with paleoanthropologists and geologists, but this is the first time they have worked with geophysicists." The project has inspired some youngsters to develop a potentially life-changing interest in science-with one even traveling to KAUST to study.

The results of this research suggest that the Olduvai Basin, once considered shallow, is more than 400 meters deep, almost twice as deep as boreholes were able to penetrate. This indicates that the bedrock lining the basin may be around four million years old, and that environments suitable for hominins may be equally ancient: "much older," says Hanafy, "than previously extrapolated from exposed rocky outcrops." The base layers of the basin were probably derived from nearby volcanoes, which may have influenced the environment, including water availability, in the distant past. This in turn would have impacted upon early hominids, who needed "water, a favorable climate, trees for protection and open plains for foraging, all of which were provided at Olduvai," explains Hanafy.

A new documentary

In Lasting Marks, a celebrated documentary about this work, the University of Liverpool's Ian Stanistreet argues that seismic imaging helps us understand the entire makeup of Olduvai: geological, climatic and otherwise. The changing climate has proven a challenge to mankind throughout our history: if we can better appreciate this history, we may be moved to alter our trajectory. As the director of Lasting Marks, Sarah Schuster-Johnson, eloquently explains, "the dedicated and passionate Olduvai researchers carefully interpret marks from an undeciphered history, a history that paved the way for our existence and our future on this planet."

Source: King Abdullah University of Science and Technology [January 21, 2018]