- Author: Kathy Keatley Garvey
If you've been following the innovative work of agricultural entomologist and remote sensing technology researcher Christian Nansen, associate professor of entomology at the University of California, Davis, you can.
Using Skittles (candy), magnolia leaves, mosquito eggs and sheets of paper, Nansen explored how light penetrates and scatters--and found that how you see an object can depend on what is next to it, under it or behind it.
He published his observations in a recent edition of PLOS ONE, the Public Library of Science's peer-reviewed, open-access journal. He researches the discipline of remote sensing technology, which he describes as “crucial to studying insect behavior and physiology, as well as management of agricultural systems.”
Nansen demonstrated that several factors greatly influence the reflectance data acquired from an object. “The reflected energy from an object--how it looks-- is a complex cocktail of energy being scattered off the object's surface in many directions and of energy penetrating into the object before being reflected,” Nansen pointed out. “Because of scattering of light, the appearance--or more accurately the reflectance profile--of an object depends on what is next to it! And because of penetration, the appearance of an object may also be influenced by what is behind it!”
“The findings are of considerable relevance to research into development of remote sensing technologies, machine vision, and/or optical sorting systems as tools to classify/distinguish insects, seeds, plants, pharmaceutical products, and food items.”
In the PLOS ONE article, titled “Penetration and Scattering—Two Optical Phenomena to Consider When Applying Proximal Remote Sensing Technologies to Object Classifications,” Nansen defines proximal remote sensing as “acquisition and classification of reflectance or transmittance signals with an imaging sensor mounted within a short distance (under 1m and typically much less) from target objects.”
“Even though the objects may look very similar--that is, indistinguishable--to the human eye, there are minute/subtle differences in reflectance in some spectral bands, “ Nansen said, “and these differences can be detected and used to classify objects.”
With this newly published study, Nansen has demonstrated experimentally that imaging conditions need to be carefully controlled and standardized. Otherwise, he said, “penetration and scattering can negatively affect the quality of reflectance data, and therefore, the potential of remote sensing technologies, machine vision, and/or optical sorting systems as tools to classify objects. “
Nansen described the rapidly growing number of studies describing applications of proximal remote sensing as “largely driven by the technology becoming progressively more robust, cost-effective, and also user-friendly.”
“The latter,” he wrote, “means that scientists who come from a wide range of academic backgrounds become involved in applied proximal remote sensing applications without necessarily having the theoretical knowledge to appreciate the complexity and importance of phenomena associated with optical physics; the author of this article falls squarely in that category!”
“Sometimes experimental research unravels limitations and challenges associated with the methods or technologies we use and thought we were so-called experts on,” Nansen commented.
Nansen, who specializes in insect ecology, integrated pest management, and remote sensing, joined the UC Davis faculty in 2014 after holding faculty positions at Texas A&M, Texas Tech and most recently, the University of Western Australia.
- Author: Kathy Keatley Garvey
Devoted to research, teaching and public service, he'll speak next week on “Urban Food Production in the Digital Age—Local Empowerment and Sustainability” as part of the UC Davis Community Book Project, which focuses on award-winning writer, activist and academic Raj Patel's work, Stuffed and Starved: The Hidden Battle for the World Food System.
Nansen, an agricutural entomologist with the UC Davis Department of Entomology and Nematology, will deliver his presentation from 12 noon to 1 p.m., Wednesday, Jan. 18 in the Memorial Union's Garrison Room, UC Davis campus.
Sustainable pest management solutions in agricultural systems is a key component of Nansen's research, and he and his team focus on deployment of drones and imaging systems to optimize stress detection of pest outbreaks. In his leisure time, he is converting his back and front yards in Davis "into an urban farming system."
In his Jan. 18 seminar, Nansen will cite several important reasons why urban and suburban citizens "should increase their level of self-sufficiency and resilience when it comes to food production."
In many respects, Nansen is a citizen of the world.
Born and educated in Denmark, Nansen received his master's degree in biology from the University of Copenhagen in 1995 and his doctorate in zoology from the Royal Veterinary and Agricultural University in Denmark in 2000. He accepted positions in Portugal, Benin, United States, UK and Australia before joining the UC Davis Department of Entomology and Nematology in January 2015 as an assistant professor who focuses on insect ecology and remote sensing. His international experience also includes being an international exchange student at the University of Lisbon, Portugal and a visiting professor at Northwest A&F University, Yangling, China.
As part of his undergraduate studies, Nansen took time off to travel to Brazil to write a book about sustainable agriculture in rainforest areas. “In this process," he related, "I learned about the potential of honey bees as both pollinators of crops but also as ‘promoters' more broadly of sustainable agricultural development."
For his doctorate, his interest turned to the larger grain borer, a serious pest of stored maize and dried cassava roots. He wrote his dissertation on “The Spatial Distribution and Potential Hosts of the Larger Grain Borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), in a forest in Benin, West Africa.” His research involved stored product insect ecology, field trapping with pheromone traps, experimental work on pheromone production, vegetation analysis, satellite image interpretation, laboratory infestation of potential breeding substrates, and histological studies.
Nansen recalled that his childhood exposures to international scientists played a major role in his choice of a career. His father, a professor in veterinary parasitology, entertained many colleagues in the family home. “And my mother cooked the food! This is probably the main reasons why I enjoy both cooking and why my career has been so international.”
“Even though Denmark is a very small country (5 million people),” Nansen said, “it has been at the forefront of agricultural research and production for many decades. And growing up, my father took me on field trips and exposed me to farming systems.” In fact, young Christian earned his weekly allowance in the chicken business: he sold eggs to neighbors.
In an earlier interview, he expressed delight at seeing a “steadily growing appreciation for the origin and quality of the food we eat," noting that "today, in the 21st century, the technologies deployed in modern agriculture are so advanced and similar to the cutting-edge technologies in other fields. Those technologies require skill sets beyond what most people may be aware of. Use of drones, remote sensing, GIS models, mathematical models of weather, crop physiology and soil dynamics, models to optimize input requirements and minimize economic risks, phone apps to optimize applications of agro-chemicals – these are all skill sets and approaches we are using as part of studying food production systems and developing innovative and reliable tools to be used within the agricultural sector.”
On Thursday, Jan. 19, the day after the UC Davis Community Book Project presentation, Nansen will give a seminar on "Droplets of Evolutionary Biology: Theoretical Modeling of Resistance Evolution to Insecticides" from 4:10 to 5:30 p.m. in 100 Hunt Hall as part of the UC Davis Evolution and Ecology winter-quarter seminars.
He is also coordinating the UC Davis Department of Entomology and Nematology's winter seminars. As part of those seminars, he'll speak Wednesday, March 1 from 4:10 to 5 p.m. on "Reflectance Profiling as a Tool to Study Insects and Other Objects" in Room 122, Briggs Hall.
All the presentations are free and open to the public.