Branching out

By Noga Martin

When Dr. Diriba Nemera finished his BSc at Jimma University in his native country of Ethiopia, he was offered a job there as a technical assistant. Realizing he needed to improve his skills and knowledge to support students as a supervisor, he began looking into graduate programs in countries that were doing “a great job with agricultural science.”

This led him to the Hebrew University of Jerusalem’s Robert H. Smith Faculty of Agriculture, Food, and Environment in Rehovot, across the street from the Weizmann Institute. In October 2012 he arrived in Israel to begin his studies. Because student visas at the time did not include spouses, his wife, Kasech Oljira, had to stay behind in Ethiopia.

As an MSc student working under the supervision of Dr. Avi Sadka at Hebrew University and Dr. Shabtai Cohen from the Agricultural Research Organization-Volcani Institute in Rishon LeZion, Dr. Nemera helped launch a multi-year project to reduce water consumption, enhance agricultural projectivity, and improve fruit quality in orchards using a novel type of netting.

Agricultural challenges in this part of Israel include high radiation load accompanied by atmospheric and soil droughts, which can limit orchards’ productivity by affecting physiological processes like photosynthesis.

“To overcome these challenges, we deployed nets of different colors and textures designed to enrich the canopy with red and blue light bands by filtering out other bands that primarily contribute to heat load,” he explains.

Dr. Nemera and his colleagues proved that reducing overall radiation load and photo-selecting the radiation bands that reach tree canopies can reduce water use by up to 40% without damaging the trees or hurting their yield.

While their study was conducted on orange trees, Dr. Nemera is optimistic that the technology can be modified to different types of orchards based on the requirements of each crop. In addition to yielding valuable insights, which continue to be published in academic journals, the project netted Dr. Sadka and the co-authors a patent for the technology.

Biosphere meets atmosphere

After Dr. Nemera completed his MSc in 2014, he returned home to Ethiopia. Three years later, upon deciding to pursue a PhD, he came back to Israel and to Hebrew University, this time with his family. He and his wife now have three children, and they live in Rehovot.

His PhD project evaluated strategies to mitigate damage to avocado orchards caused by long-term irrigation with treated wastewater. His supervisors for this project were Dr. Asher Bar-Tal and Dr. Cohen (both at the Volcani Institute), the latter of whom was collaborating with Prof. Dan Yakir from Weizmann’s Department of Earth and Planetary Sciences.

After attending a seminar hosted by Prof. Yakir’s ecophysiology lab, Dr. Nemera became fascinated by their work. The Yakir group studies interactions between the biosphere and atmosphere across different scales and environmental conditions with the goal of understanding the processes behind how ecosystems in dry climates respond to local and global climate change, and how they interact with other ecosystems and climates. Dr. Nemera began a postdoctoral fellowship with the group in May 2021. (Read more about research in the Yakir lab on page 4.)

Desert rain

Using an experimental set-up in Israel’s largest planted forest—Yatir Forest on the edge of the Negev Desert—Dr. Nemera is studying how drought affects trees’ physiological response to environmental changes, especially in semi-arid environments. Hot, dry countries like Israel are confronted with two main types of drought. Atmospheric drought is characterized by high vapor pressure deficit along with high radiation load and higher temperatures. The second type, soil drought, is caused by low or erratic rainfall. He explains that soil drought is a “major factor” in Israel, with the Yatir Forest seeing a few months of rain a year that culminate in about 288 millimeters of rainfall.

To study how tree physiological responses react to drought conditions, he and his colleagues simulate changes to rainfall levels by manipulating irrigation levels. For the first few years, the trees were fully irrigated. Then, the group gradually reduced the water output, and now they are studying the physiological mechanisms that enable plants to adapt to changing environmental conditions and how climate change affects these mechanisms themselves.

Dr. Nemera aspires to establish his own research lab focused on climate change in the context of agricultural sustainability and hopes to make a lasting contribution to efforts to counter this global threat.

“We can no longer deny climate change,” he says.

Motivated to stay

The tragic events of October 7, 2023, left Dr. Nemera and his family shocked and grieved, he shares. Under the heavy rocket fire that followed the initial attacks, his young children struggled to understand the situation. However, he notes that his belief in God and faith in the “effectiveness of the Israeli air defense system” gave him some peace of mind about his family’s safety, although the conflict proved to be more prolonged and challenging than he anticipated.

“The general unwavering emotional support and encouragement from colleagues at the Weizmann Institute, including administrators, my PI, and lab mates, provided additional motivation for me to stay and continue my research despite the difficult circumstances,” he says.

HOW WAR AFFECTS AGRICULTURE

War can have a severe impact on both the environment and agriculture, resulting in disastrous consequences. Firstly, war can involve the destruction of critical agricultural infrastructures and contamination of land, rendering it unfit for agricultural use. Displacement of farmers due to conscription and forced relocation disrupts established agricultural practices and reduces the available labor force, further hampering productivity. Economic disruptions exacerbate these challenges by jeopardizing market stability and hindering access to essential agricultural inputs.

Consequently, food and nutritional insecurity escalate as production diminishes and distribution networks weaken. Moreover, environmental damage such as deforestation and land degradation worsens the already dire situation, leading to long-term consequences for biodiversity and ecosystem health. The breakdown of social and institutional support systems compounds these challenges, as governments and aid organizations struggle to provide effective assistance amidst the chaos of war.

Rehabilitating agricultural systems and restoring environmental health become difficult tasks, prolonging the suffering of affected communities and further delaying the return to peace, stability, and prosperity. – D.N.