This Google Earth Tool is Changing Land Planning

Remote sensing expert and retired UC Davis Proffessor Dr. Susan Ustin discusses how data driven land monitoring can support sustainable urban and agricultural design

Photo courtesy of Geospatial World

Resources across the globe are often misinterpreted, unknown, or mishandled. As Climate Change continues to urge urban regions to expand and reform, higher technology environmental science tools are needed at a more urgent rate than ever. From infrastructure placement to irrigation arrangements that take into account the protection of ecosystems and evenly distributing the limited resources among us, we can look to developing technology to lead the way. Remote sensing is the science of gathering land data from satellites, aircraft, and drones to monitor and track the surface of the Earth from afar.

Not only does remote sensing help scientists and policymakers effectively comprehend and visualize present land use, agricultural health, and urban undertaking; but it also helps predict future ecological trends with high accuracy. In regions like California, where farmland and urbanized regions often stand shoulder-to-shoulder, this technology is incredibly relevant in ensuring industrialization and urban development is sustainably backed. 

Dr. Susan Ustin, a professor emerita at the University of California, Davis, is a leading expert in environmental remote sensing. She directed the Center for Spatial Technologies and Remote Sensing (CSTARS), and has published over 200 papers on topics including vegetation ecology, land use, and precision agriculture. Her collaborations with NASA, including work on hyperspectral imaging missions such as AVIRIS, have advanced tools which can be used to monitor biodiversity, drought, and crop health. Her research has shaped eco-friendly water use in agriculture, encouraged climate-resilient land planning, and aids in protecting natural habitats worldwide.

In this Q&A, Ustin explains how remote sensing is transforming our understanding of both urban and agricultural landscapes and newer development; and how it can help in paving the way for a more sustainable future.

Q: How has your remote sensing work informed or influenced actual public policy, whether that be through smaller agencies such as SACOG, or other local governments?

A: In particular, we've had several projects with different resource agencies at the State Department of Water Resources, fish and wildlife, and Air Resources. So we have worked on using remote sensing to in particular in the Delta, in the Sacramento San Joaquin Delta. For 20 years, we had an airplane fly the Delta with a hyper spectral imager, which is an instrument that measures many spectral bands in every pixel for 20 years to monitor the locations of different aquatic weeds in the Delta that the state has to manage. And we have developed for the Department of Water Resources a program to use the geospatial satellite to get an estimate every day, once a day, for the potential evapotranspiration for the whole state. What's been going on for 25 years, almost. It's used by many, many people who want to try to help farmers, especially to not over irrigate their plants. They can wait a day or a few days. And so that's important for that. And in terms of other atmospheric gasses, we've worked with the Air Resource Board on certain kinds of gas emissions that are occurring, they have to monitor, like methane. That's a variety of things for both mapping individual species like weeds and agriculture, weed species in agricultural fields for farmers, and looking at whether the plants are water stressed and need to be irrigated. 

Q: Your findings on urban heat islands and tree canopy inequities in more urban neighborhoods are very relevant to climate justice in the modern day and age. What sort of policy changes do you think cities should prioritize in a response to this data?

A: Well, planning departments can do a lot with this kind of data to try to reduce the need for additional air conditioning in the summer by encouraging tree plantings in neighborhoods that don't have them. So you have more trees for the purpose of shade, things like that. They can look at if you have the trees in the yards, or if you don't have them, you have different types of runoff issues. Those are the kinds of issues, mostly health related, but it's also quality of life related. I live in a part of Davis that has village homes, which is has very narrow streets, and it was designed to be energy efficient, and it's noticeably cooler because of all of the trees…but of course, they there's kind of a conflict in that sense, that they also use water in the summer in order to transpire water. And so there's this if you want to plan for less water, then you probably want fewer plants, and especially trees. But if you want to have a more comfortable life, you pay for it one way or the other so they're trade-offs. But they can use this kind of information to determine the kind of environment that they are in. And usually neighborhoods that have more vegetation and more trees are more expensive. I mean, the houses have higher value. So that is my incentive to want to do that.

Q: What are the benefits and limitations of hyperspectral imaging as compared to other forms of remote sensing?

A: Well, it has a lot more data, so it requires more capabilities for analysis. But right now, the US doesn't have a satellite that has a hyperspectral imager on it. Actually, the Europeans have two satellites with this capability and a company called Planet, has been specifically doing methane emission detection, but it's actually capable of using the whole spectrum, not just the parts of the spectrum that were methane. And so, a part of the limitation has been that we've been available on airplanes for many years, and also just been very slow to launch it on a satellite. We have one that was expected to launch in 2028 NASA just canceled the program. It's three quarters built copy about that I guess their budgets are being cut. And so that was one of the programs that was killed. So, yeah, the Europeans are going to be launching Landsat, like a satellite, meaning it'll have routine, like a weekly to monthly, operational ability to get hyperspectral data that will be launched sometime this decade, before 2030. And we will have access to it, because it's free and open access to the data, so we can use it and we can rely on that, that one.

Q: Your team has mapped evapotranspiration in urban and agricultural systems in the past. How can this kind of data help cities and urbanized areas to adapt to drought conditions or extreme heat events?

Knowing where and how water is being used can help us to help planners better understand where water is, where water is needed and where it's lacking, so they can better manage those resources. Obviously, when the plants are very severely drought stressed, that's when we have fires. And it isn't a predictor of fire, because basically, if at the end of the summer, when the plants have not had rainfall for months, they're all drought stress. But it just says that if a fire ignition starts somewhere. There's a high probability that it can become a large fire, so that it can be used to look at risk, but not necessarily predicting where it's going to happen, because the ignitions could happen from lightning or from a human starting it, but it could at least tell how much at risk whole areas are. Of course, we're limited by the weather, and there's not a lot that can be done, but they can better plan how to protect people's lives and plan for evacuations and to better respond when there is an emergency.

Q: As remote sensing becomes more accessible through tools such as drones and the Google Earth Engine, how should governments regulate its use while encouraging more people to get involved?

Well, drones are under the government's regulatory powers. Because they are supposed to have a license to fly them. And there're rules about not flying closer in certain air spaces and not at certain times like when there's an emergency. You don't want private citizens flying over the site that might cause interference with what's going on. So those are kind of practical rules. The Earth Engine available for anybody that wants to use it, right? So there really are no restrictions on access. It's a matter of understanding being able to know how to use the programs, learning process involved but anyone, in principle, could go online and go to Earth Engine and use that data. And actually that's a good thing, because it means private citizens can see what's going on if they don't believe it in the newspapers. But at the same time, I think there should be privacy restrictions too, so that most of the data at Earth Engine is not higher spatial resolution, where you can recognize somebody, or those kinds of things. But there are some issues, especially with drones where you're not supposed to be flying and looking into people's windows. But those are, I think those are regulatory issues that that, and I think there's, there's quite a few. Sometimes people don't obey the rules, right?

Q: Land cover classification is a key theme in your work. Can you talk about how remote sensing helps distinguish between different vegetation types or land uses, especially in complex urban environments?

A: Yes, well, the urban environments are not different in principle from other environments. It's just more complicated. But basically you're relying on how different objects absorb and reflect light differently in parts of the electromagnetic spectrum. You couldn't tell them apart, but it's because of a combination of their chemistry and their structure. So how the canopies are arranged is the structure and the chemistry is mostly chemistry of the leaves. And even though living plants all have green leaves, because they have chlorophyll in them, they vary in the amount and different chemicals, even though they're they more or less share the same basic metabolites. So conifer trees and herbaceous little flowers or something there, they have the same basic metabolism, but they aren’t in the same position. So how much different pigments that are involved in photosynthesis that are in that chemistry, proteins, sugars, starches and cellulose that are in the cell walls and the cells and so on; that all of those things affect the how it absorbs and reflects light in different parts of most remote sensing using visible light, that's that eyes can see, and the infrared, near infrared, so it all comes from the energy coming from the sun. Now you can get wavelengths, and you're measuring thermal emissions. That's the energy that objects that are emitting energy based on temperature, and then along your way, you have a radar so different parts of the spectrum have different information, and multiple bands satellite that measure different parts of the spectrum or difference, like radar versus hyperspectral and measure the visible, linear infrared, they are seeing different things. And so by combining that information, you can tell many different things. And one of the things that the structure does is that  different shading also happens because of the way that canopies. Yeah, they look different in the image. They have different values. And use that pattern, the spectral pattern of what it usually looks like in different wavelengths. This is one thing from another. So that's what has been done, and it's simpler. Say you have a corn crop, and everything in your corn crop is all the same age, it's more or less the same size, and it's very uniform. So in that field it looks almost identical, but where the plants aren't watered, or you have invasive species or some weeds, they look different. And where hyperspectral breaks off, you have 200 bands instead of five, and with that, you have a lot more information to differentiate from another.