The Acacia Tree Stars in the Arava Ecosystem

Thursday, November 19, 2015 10:56 AM

“The acacia is the only indigenous tree in the Arava, and its contribution to the ecosystem is vital, whereas the entire complex of flora and fauna depend on it.”

Distinguished research scientists from Israel and abroad addressed many topics related to the acacia tree at the third annual conference on Acacias in the Arava: Past, Present and Future. The two-day conference (11‑12 November 2015), organized by the Dead Sea & Arava Science Center (DSASC) and sponsored by Ben Gurion University of the Negev, was held at the Vidor Center – A Window to Agriculture in the Arava, which was established with the support of Friends of JNF Australia.

Participants of the third annual conference on the Acacia, in Nahal Shita in the Arava. Photo: Yoav Devir

An acacia trees grows outside the Vidor Center in the Arava. Photo: Yoav DevirAmong the topics addressed at the Acacia conference at the Vidor Center were the physiology, genetics and microbiology of acacia trees, the wildlife in their environs and the use of remote sensing for mapping and monitoring them. One of the main topics was the devastating oil spill in the Ein Evrona nature reserve in December 2014, which accentuated the delicate balance of the singular ecosystem of the Arava, which is dominated by the acacia tree.
The first day of the conference included presentations by leading experts, and the second day featured tours of the three main acacia research stations in the Arava: Nahal Shizaf, Nahal Shita and Ein Evrona. The station in Nahal Shita was founded by KKL-JNF and engages in monitoring and in long term ecological research (LTER).
DSASC scientist Dr. Gidon Winters. Photo: Yoav Devir“The acacia is the only indigenous tree in the Arava, and its contribution to the ecosystem is vital, whereas the entire complex of flora and fauna depend on it,” said DSASC scientist Dr. Gidon Winters, one of the initiators of the conference. “The acacia provides food for a variety of animals, upgrades the soil for the benefit of other plants, and its deep roots contribute to the stability of the ground and prevent erosion.”
Indeed, even if you are no expert, when you tour the region, it is not hard to notice the different species of plants growing around the acacia trees and attracting birds and insects.
Norweigian biologist Prof. Knut Krzywinski in Nahal Shita. Photo: Yoav DevirAmong the conference participants was Prof. Knut Krzywinski, a biologist from the University of Bergen in Norway, who is prominent in this field. He has conducted research studies on acacia trees in Sudan, Libya and Egypt, but he is particularly interested in Israel, since it is the northern extremity of acacia proliferation.
Speaking about the significance of the conference, Prof Krzywinski said, “The meeting of research scientists from different places and diverse fields is the best way to advance scientific knowledge, especially when addressing ecological issues. Only this kind of gathering can help us see the big picture. We talk, we share ideas, we exchange data, and sometimes we even argue.”
Day One: Acacia Trees and Ecology
Examining mistletoe growing growing on an acacia tree. Photo: Yoav DevirThe conference opened with greetings from Dr. Hanan Ginat, a research director at DSASC; Dr. Gidon Winters and Ami Uliel, KKL-JNF Southern Region Director. The first session, chaired by Prof. Knut Krzywinski, dealt with community ecology. Dr. Benny Shalmon from the Israel Nature & Parks Authority (INPA) spoke about the interaction between acacia trees and ants. Dr. Yael Lubin from the Blaustein Institutes for Desert Research (BIDR) at Ben Gurion University spoke about the affection of social spiders for acacia trees. Dr. Leo Zwarts, an ecological consultant from Norway, spoke about the preference of forest birds for acacia trees. Dr. David Ward from Kent State University, USA, addressed the question of whether or not mistletoes kill acacia trees.
An acacia sprouting in Ein Evrona, unlikely to survive due to pollution in soil caused by oil spill in December 2014. Photo: Yoav DevirThe second session, chaired by Dr. Elli Groner from DSASC, focused on landscape ecology. Yael Rodger from BIDR spoke about the genetic construct of the two acacia species found in the Arava, the twisted acacia, Acacia raddiana, and the umbrella thorn acacia, Acacia tortilis. Heidi Andersen from the botanical garden at the University of Bergen in Norway spoke about the differences between acacia populations east and west of the Nile. Yehoshua Shkedy from the INPA spoke about a topic addressed by many of the conference participants—how to deal with the damage done by the ecologically disastrous oil spill in Ein Evrona. Sivan Isaacson from the Geography Department at Ben Gurion University presented tools for remote sensing that enable monitoring acacias both from the ground and from outer space.
The third session, chaired by Dr. Gidon Winters, focused on acacia physiology. Prof. Knut Krzywinski showed how advanced technological tools enable data gathering for acacia trees. Dr. Dennis Otieno from the University of Bayreuth in Germany described the strategies of acacia trees for coping with drought. Dr. Hanan Ginat spoke about the acacias in the most arid regions of southern Israel. Dr. Ina Ryvkin from DSASC spoke about mapping subterranean strata using electrical resistance tomography (ERT). Dr. Gidske Andersen from the University of Bergen in Norway presented a research study on acacia seeds in the Sahara Desert.

Visiting an acacia research station in Nahal Shizaf in the Arava. Photo: Yoav Devir

The fourth and last session of the day, chaired by Dr. Hanan Ginat, focused on the ecology of acacias in the Arava. Liraz Cabra from the Society for the Protection of Nature in Israel (SPNI) spoke about the unfortunate disappearance of the Red Sea warbler, Sylvia leucomelaena - the small songbird of the Arava. Dr. Elli Groner from DSASC spoke about establishing the LTER station in Nahal Shita. Dr.  Nizan Segev, also from DSASC, described the destructive consequences of the oil spill in Ein Evrona. Prof. Knut Krzywinski presented models for measuring the age and growth rate of the umbrella thorn acacia in the Arava, based on radiocarbon dating.
Day Two: A Field Day
Walking between the acacias in Nahal Shizaf. Photo: Yoav DevirOn the second day of the conference, the research scientists quit the lecture hall and went outdoors to see the research stations in Nahal Shizaf, Nahal Shita and the Ein Evrona nature reserve. They were accompanied by students from China and Vietnam who are studying and practicing agriculture at the Arava International Center for Agriculture Training (AICAT).
Dr. Gidon Winters noted the different studies being conducted in Nahal Shizaf on the acacia and on local wildlife such as birds, butterflies and insects. “The researchers are trying to develop objective methods for assessing the success rates of the trees by analyzing photographs and observing the changes in the color of the leaves,” he explained.
Dr. Denis Otiento demonstrates the sensors attached to the acacia tree that measure the moisture in its branches in Nahal Shizaf. Photo: Yoav DevirDr. Denis Otieno presented sensors that measure the fluid flow in the branches of the acacia tree. As he sat in the shade of the acacia tree, with his laptop connected to sensors attached to the tree, one could appreciate the tangible example of technology and nature working well together.
Liraz Cabra demonstrated how she locates the Red Sea warbler by playing a recording of the twitter of the male, next to acacia trees, and waiting for the birds to respond with their pretty tweets.
The group proceeded to Nahal Shita, where KKL-JNF has established a station for long term ecological research (LTER). “The research studies done in this area focus not only on the trees but also investigate the terrain comprehensively,” said Hannah Bechar, Director of the KKL-JNF Southern Region Forest and Community Division. “Assisted by these studies,” she said, “we are learning about the acacia, how it is affected by the environment and how it affects the environment.”
Harvested floodwater remaining from recent flashfloods in the Arava. Photo: Yoav DevirKKL-JNF provided the scientists with old photographs of the region so that they could compare past conditions with the data gathered recently by monitoring the ecosystem.
“We are hoping to involve the community in the research,” said Bechar, “and to encourage local residents to become actively involved in data gathering in a program called Citizen Science.”
Dr. Hanan Ginat presented photos of the flooding in Nahal Shita this winter and asked, “How is it possible for trees to survive in such an arid climate?” He answered, “Because of their deep roots, the floodwater supplies them with life for a number of years, until the next flood.”
Dr. Elli Groner noted that the research studies in Nahal Shita are investigating the connections between biodiversity, plant biomass and environmental conditions. Following all the scholarly explanations, the members of the group dispersed for independent observation of the area so that they could get their own impressions of the acacias and of the flora and fauna in the vicinity.
Oil stains remaining in Ein Evrona nature reserve from the oil spill in December 2014. Photo: Yoav DevirThe last stop on their itinerary was the Ein Evrona nature reserve, which was badly harmed last year by the disastrous oil spill in December 2014. Five million cubic meters of crude oil polluted an area of 14 hectares in the nature reserve. KKL-JNF assisted by providing a primary response during the huge oil spill, with tractors and heavy equipment that was being used for the development of infrastructure for the new Ilan Ramon Airport, currently under construction next to the nature reserve. The equipment was dispatched immediately for digging pits to mitigate the flow of petroleum and prevent far greater damage.
Today, too, one year after the ecological disaster, one can still see the oil stains on the ground, and although the flooding this winter has erased those black marks, there is still a deep layer of crude oil beneath the surface. This is evident when you pour water on the ground, and it does not seep into the earth but floats above the petroleum without penetrating the soil. Not far from there, one can see remains of an oil spill that occurred forty years ago, the 1975 ecological disaster.
Dessicated acacia tree in Ein Evrona due to oil spill. Photo: Yoav DevirNizan Segev, the monitoring coordinator in Evrona for DSASC, gathered the members of the group around one of the acacia trees that had desiccated and died due to the 2014 oil spill. “Trees are dying, new trees can’t grow, and scientists have reached the conclusion that if we don’t clean away the petroleum in the area, we can expect the population of acacia trees in the polluted area to decrease to the point of extinction,” she said.
Asaf Habari, INPA Director of the Eilat Region, noted that experimentation is being done at present to explore methods for cleaning the area and reducing the damage caused by the oil spill, using bacteria, chemical substances and cultivating the ground so that floodwater will wash away the pollutants. The removal of polluted soil is not under consideration at the moment, because topographical changes could cause additional ecological damage.
Taking soil samples in Ein Evrona. Photo: Yoav DevirJust before the group left the nature reserve and closed the conference, a herd of gazelles passed by. The exquisite animals stopped next to one of the acacia trees as if to confirm what the experts had been saying about the central role of the acacia tree in the ecosystem of the Arava. Seeing the gazelles in the nature reserve could remind us all that while people may cause ecological damage, if we work together with responsibility and concern for the environment, perhaps we will be able to remedy the ecological damage done and preserve the world for our own sake and for the sake of future generations.