Letitia Grenier is the principal investigator for the San Francisco Estuary Institute’s Delta Landscapes project, which recently completed an in-depth analysis on the change in the Delta overtime and is now offering science-based guidance on how the Delta’s ecosystem health can be recovered as part of a working landscape. Ms. Grenier is one of a number of authors on the paper, The Delta as Changing Landscapes, for the State of Bay Delta Science 2016.
“This paper is very much focused on using landscape ecology and landscape science to think about the Delta,” Ms. Grenier began. “All these different images are different layers or different types or data you can think about for the landscape scale analysis and understanding of this place. I think it’s one of the strengths of our Delta Landscapes overall. We really took a large-scale integrated systems view; it’s very much not about a single species or a single habitat type, it’s how does this big system work at the landscape scale. If you think about it that way, from the base physical functions that create some of the template for the ecological functions that we want, such as supporting our native wildlife or supporting particular fish, that gives us a different insight into what we might want to do as we think about restoring some of these functions in the Delta.”
There were three phases to the Delta Landscapes project with three reports produced. The first report in the series was the Sacramento-San Joaquin Delta Historical Ecology Investigation: Exploring Pattern and Process which focused on how the system used to function in the past, prior to really intense modification of the landscape after European settlement of the Delta. The second report, A Delta Transformed: Ecological Functions, Spatial Metrics, and Landscape Change in the Sacramento-San Joaquin Delta analyzed the changes between the historical Delta and the modern Delta. The third report, A Delta Renewed: A Guide to Science-Based Ecological Restoration in the Sacramento-San Joaquin Delta offers visions for how the Delta could be restored, thinking at the landscape scale.
The paper published for the State of Bay Delta Science 2016 is really an implementation of those ideas. “If we think about the structure and function of landscapes, if we use that body of science and apply it to some of our problems in the Delta, what would we come up with for answers?,” she said, presenting a slide with quotes, and pointing out that the need for taking a landscape view of the Delta has been acknowledged by several previous documents about the Delta. “We’re not just coming out of science left field here, but we’re actually relating to the water code and to the Delta Plan, so this is really about taking a landscape perspective, thinking across large scale, thinking across large spatial scales, and about the connectivity of the habitats in the landscape, and sometimes the disconnectivity.”
Ms. Grenier pointed out that the different types of landscapes in the Delta have not been affected in the same way; the way the wetlands and upland habitats have been affected is really different than the way that the water and aquatic habitats have been affected.
Around 1800, the Delta at the time had similar channels, but it was a big wetland. The form of the channels was different as was what was in between the channels; there were ponds, there were riparian areas around the fluvial channels and in between there was marsh, most of it tidal marsh.
The Delta today has almost been completely transformed. The only thing that is really recognizable is some of the shapes of the channels, but everything else has pretty much changed, she said.
From a landscape perspective, the way the system used to function historically was that there were these very big drivers of the physical process; as well as climate and geology and other factors that were different across this Delta. Ms. Grenier reminded that it’s a very big system, and this is only the upper part of the estuary.
The Sacramento River and the San Joaquin River both flow into the Delta; they have different flow regimes, timing, and climates; there are other smaller rivers that also flow into the Delta, creating gradients of sediment supply, temperature, and chemical gradients coming into the center of the Delta. Historically, there was a unique giant inland marsh behind the constriction point at the Carquinez Straits.
“It wasn’t all the same across the north, middle, and south of the Delta; they were quite different landscapes,” she said. “In the north, you had a landscape that was really driven by the fluvial processes of the Sacramento River, so there was a very high sediment supply. There were big basin floods that lasted for months going down each side of the river so there was incredible floodplain productivity. In the central Delta, it was much more of a tidal marsh driven system with large marsh islands; there weren’t as many high natural levees so it was more tidally-dominated rather than fluvially-dominated. In the south Delta, it was more of a complex habitat mosaic; a different kind of timing for the flooding, and there tended to be more oxbows and off-channel aquatic habitat. So it wasn’t really homogenous. It was a complex place.”
To ensure use of the best available science, the Delta Landscapes project relied on a science advisory panel called the Landscape Interpretation Team, which was comprised of experts on a lot of the different aspects of the biology, and physical processes in the Delta.
She presented a graphic depicting their approach to the landscape analysis for the Delta. They first determined the desired ecological functions, or the things that the Delta isn’t doing that people want it to do, and those are shown in the yellow row. Five of those functions are around taxonomic groups: supporting native wildlife, supporting native fish, supporting native marsh wildlife, supporting connectivity and habitat for waterbirds. Community-level functions are on the right, and include things such as the Delta not supplying enough food or not supporting other aspects of diversity, or not being able to allow wildlife populations to evolve via natural selection over time.
In thinking about how to analyze the changes in the landscape, they determined the metrics that were used to measure that change. Landscape ecology typically has metrics like patch size, connectivity, size to area ratios, but they realized that simple landscape ecology metrics weren’t adequate for the analysis needed for the Delta.
“So what we had to do was layer them really carefully and say how much edge habitat do we have between riparian of a certain kind of structure and composition of species with a certain width and a certain length down the river that’s next to marsh that’s actually hydrologically functional,” said Ms. Grenier. “That’s the kind of thing we had to get to in order to really analyze the landscape in a way that would relate more directly to these functions. It turned out to be a very intensive process of understanding the biology and then interpreting that as change in the landscape.”
The report, A Delta Renewed, tries to provide some visions about how you could restore the desired ecological functions, she said.
Ms. Grenier then gave some examples of the change analysis of the Delta to see how landscape science helps to understand the changes that have been made. She presented a map contrasting the habitat types and land use in the historical Delta to that of the modern Delta. “You can see there has been pretty much a trade-over of green for pink, which is marsh, mostly tidal marsh for agricultural,” she said. “At a simple level, that’s a really good base understanding of what’s happened here. They are both very productive kinds of habitat or land use, but one services native wildlife and the other services mainly people, although there is some really neat stuff going on with wildlife and agriculture as well. The bar chart is showing the change in those two major habitat types or land uses, as well as minor changes.”
Landscape change is not just change in habitat types or extents, or their configuration on the landscape; but there have also been changes in the physical processes that create and maintain those landforms. “In a lot of our lifetimes, if you created a marsh, it might remain a marsh for about 20 to 30 years and that was true since we’ve been doing a lot of wetland restoration in California,” she said. “But now things are changing, especially with climate change, and we can’t expect that by creating static habitat types anymore, we’re actually going to maintain that place and that kind of function over time. Instead we have to realize that we need to restore the underlying physical forces that make that habitat resilient; so for example, if you want to restore the marsh, you may need to restore the sediment supply and the tidal action that allows that marsh to accrete and grow vertically as sea level rises. That’s certainly one thing we think about in the bay; it’s going to be just as relevant in the Delta.”
Historically, flooding processes were critical for creating and maintaining habitats in the Delta. Ms. Grenier presented a map showing the change in flooding on the landscape between the historical and the modern Delta. She explained that the different colors of blue represent the different kinds of flooding that used to occur. The dark purple-blue in the north and the south was basin flooding that was a few feet deep and lasted several weeks to a few months; it covered extensive areas and actually flooded earlier on the Sacramento River than the San Joaquin River and was a major resource in terms of activating food webs. Those food webs remaining active for several months and then they would drain slowly over time so the fish could get back into the creeks or the rivers.
In the central Delta, the medium blue represents tidal flooding, which was flooding every day more or less, and it covered a vast extent. The light blue around the edges of the Delta was more intermittent, shallow seasonal flooding, such as wet meadows. There was also some basin flooding on the Cosumnes. “There’s a huge amount of inundation; the wetland was wet a lot of the time, and it was also extremely productive,” she said. “Recent research shows how important floodplains are for wildlife and this situation was creating food all the time. Almost at any time of the year, something was flooding; certainly the tidal areas, but a lot of the basin flooding actually happened for many months because of the complex timing. This was essentially a food resource that was there for California wildlife almost all the time. Because of the complex nature of the landscape, they could go to a different place to eat in a wet year or a dry year or a hot year or a cool year. There was a lot of complexity of resources that allowed wildlife to pick and choose, based on the conditions.”
She noted the graphic is depicting flooding in fairly wet years; the basin flooding is almost completely gone, as it the tidal flooding. “What we have left is a little bit of that light blue flooding in the Yolo Bypass, and there’s also some of that more short-term not so deep seasonal flooding,” she said.
Ms. Grenier pointed out that the area that still experiences flooding are the Cosumnes and the Yolo Bypass. “They are really functional pieces of landscape. They do a lot for wildlife when they flood, so even though we’re not going anywhere near the historical conditions, we can make a big change by creating these temporary habitats that provide a lot of food and create these places for wildlife to go and to spawn and to eat. Although this exemplifies how much complexity we’ve lost and how much process we’ve lost, it also shows how much we can get back with just a few actions.”
She then presented a slide showing the change in tidal marsh, noting that the far north and south ends were not tidal, so the map on the left shows the historical marsh extent. “What you can see is that most of the marsh is gone, about 98% loss of tidal marsh, about 99% loss of marsh overall.”
She then presented a slide showing the change in riparian habitat. The historical riparian was about 100 meters wide with some big gallery forests that were 500 meters wide. “What I notice about this is that there was a lot more of it than we see today but it was also in a very coherent pattern,” she said. “It was like these hands reaching from the north and south into the Delta; there were corridors so if you were a terrestrial animal that wanted to go into the marsh to eat, you could very consistently follow the riparian corridor and basically have that edge all the way along. It was a route into the Delta.”
In today’s Delta, the riparian habitat has been heavily impacted. “On the Sacramento River in particular, those are all the nice dry places so that’s where people want to live, that’s where we wanted to put our orchards, so it makes a lot of sense that those natural levees are being used for other things,” she said. “With the riparian habitat that’s left, there are actually a lot of bits of riparian all over the place, but they’re not in a pattern that makes sense. They are in artificial levees, kind of scattershot everywhere, and so it isn’t coherent landscape anymore. If you are wildlife trying to get to the other side of the Delta, you’re just sort of lost among all these little bits. With the exception of the Cosumnes and a little bit here in the San Joaquin, there’s none of that historic riparian that can guide you in the way it used to.”
Ms. Grenier then presented a map showing open water, noting that open water is a complex habitat to talk about because not all open water is the same. “A lot of the types of aquatic habitats that were in the Delta before are actually mostly gone, and we have a lot of new novel habitat types,” she said. “A lot of them are highly invaded by non-native species, so it’s not a simple thing to say this is apples and apples. But looking overall at how much shallow water habitat there is now compared to historically, there’s about 2 times as much now as historically, so I think that’s really interesting that there’s been a lot of the focus in the last 10-20 years on the need to restore shallow water habitat to make food for fish. This map doesn’t necessarily imply that that’s going to help. I think that thinking about the changes in the types of shallow water habitat and what are they adjacent to and how much do they flood – those processed based landscape based approaches are going to help us answer this question.”
She then turned to discuss how the channels have changed, presenting a map of the historical channel network with the historical network shown in blue and the yellow-gray lines depicting the channels as they are today. “This doesn’t even actually get down to the first order channels; this is just what could be mapped from the historical data,” she said. “There were a lot of those dendritic arterial-like capillary-like networks that basically fed the marshes. They brought the water in and took the water away. There was a lot of exchange of materials, energy, and biota in those tidal cycles. The smaller capillary channels that fed the marshes, those are gone, because the marshes are gone. They’ve been turned into agriculture. In addition to that, we’ve added a lot of these cross-channel cuts to make it easier to get around and to move water around, and so we’ve really changed the plumbing of the system rather dramatically.”
Ms. Grenier said it can be hard to know what’s going on underwater, but she thinks the change in the aquatic habitat is just as extreme as the change in the wetlands and the uplands. “We used to have small channels with probably very turbid water in marshes, there was a lot of overhang of the vegetation so it would be very cool, there were places to hide, and little puddles where the water would stay when the tide drained out,” she said. “That’s all gone and now what we mostly have are these very lake-like large channels; they are very connected and the water moves them quickly. It’s almost as much of a 100% transformation as we’ve done with the wetlands but it’s harder for us to perceive that change.”
To explore the food web and primary production, with funding from the Delta Science Program and USGS, they held a workshop with a number of primary producer experts from around the country to come give their opinion of what they thought that change in those habitat types would mean in terms of primary production.
“Out of that workshop came this hypothesis of how much primary productivity there used to be from different primary producer groups historically and now,” she said. “Phytoplankton, this light blue color, has been so much the focus of thinking in the Delta because this is the productivity we have left for wildlife. But there are actually historically many other primary producers and they are still here today in lesser numbers. They contributed a large part of the total portfolio of food that was available to primary consumers. And so I think this, in and of itself, is a little bit of a paradigm shift to think about. What are the ways we could think about food for all different wildlife in the Delta? Do we need more shallow water habitat with phytoplankton? Or do we need other kinds of primary producers?”
Another big change is the loss of marsh productivity; even though it wouldn’t have been very available to consumers, because it was plant based so not as nutritious as algae, it was associated with a lot of non-phytoplankton microalgae. “All the algae that lives on the plants and on the sediment of the marsh is also gone,” she said. “The detritus that comes out of the marsh … that detritus and the things that are eating the detritus – that’s a significant amount of food, just because the total amount is so huge.”
“The two hypotheses that came out of the workshop were first that we’ve lost all this marsh-based production that might actually be valuable to various kinds of wildlife, and second that we’ve lost this diversity,” she said. “Having these many different sources might have been valuable to wildlife as conditions change, but three of those sources are just so small now, it’s hard to imagine them being important in the food web.”
As they worked towards visions for restoration, they drew on experts in landscape resilience from the academic world; they collaborated on a paper that synthesized all the landscape science from the literature around the world on resilience and put that into a really practical operationalized handbook for people who are trying to do restoration on the ground which is the landscape resilience framework.
Setting, process, connectivity: First, you really have to know your place, she said. “If our goal is to restore tidal marshland to support biodiversity and primary production, then what do we need to think about in terms of process for that restoration? We need to be at the right elevation because we think about what’s going to happen over time with climate change and sediment supply. Is our marsh going to be sustainable and resilient? Do you have the hydrology and do you have the tidal range to make a sustainable tidal marsh there? You want to make sure that you have fresh water and sediment connected to the watershed, so it’s not just the tidal process from the bay but it’s also the watershed process looking upstream. You want to think about the connectivity with both the terrestrial area nearby, so you’re going to need these broad transition zones to the terrestrial areas, and you’re going to need to think about connectivity between marshes themselves, so if you can’t put big marshes near each other, then you need to put small stepping stones in between them to link them up.”
Diversity and complexity: “It’s not just marshes in the north Delta or marshes in the south Delta; you have to restore them across key physical gradients of elevation and salinity if you want to get that complexity and diversity of function in the marshes.”
Redundancy: Create redundant functions in the Delta with taxonomic groups or habitat patches. “We’re probably going to need redundancy of large marshes, migration routes (especially for fish), floodplains, and other key landscape elements. So it’s not just one big marsh that will do the trick.”
Scale: “What we think needs to happen is bigger than what’s been conceived of in the past, and a lot of that is based on making sure we have the right scale of habitat patches so the physical processes can function,” she said. “Time scale – we can’t expect restoration to happen in five years … we need to allow habitats to evolve and we need to allow plant succession to happen, so trying to let that be okay that these natural processes are going to take more space and more time than we might like.”
People: “People are the crux of this whole ecosystem that we’re talking about in the Delta … there are a lot of stakeholders in the Delta that don’t live here as well, and so involving those people in the process so they can appreciate why these things are important and how they should be done most efficiently.”
From this landscape resilience framework, they developed a simple conceptual model to try and help people think about the expectations of what can be restored. “We’re trying to think about this system as there are these physical processes and those interact with the landscape. This is the historical view of the conceptual model. Landscape used to be intact which is what the green box is meant to show, it used to be complex, and then from the interaction of physical processes of landscape, you get these ecological functions that you want from it.”
What’s happened now is that we’ve interrupted a lot of the physical processes, she said. “We’ve changed the flows, we’ve changed the setting, we’ve changed the sediment supply, and the way things are connected. We’ve broken up the landscape, we’ve fragmented a lot of the wetlands, and homogenized a lot of the waterscape so converse actions there. We’ve created novel habitats and types of land uses and so we’re not getting all of the ecological functions any more. Some of them are all the way gone, some of them are sort of stuttering along.”
“The idea with restoration is we can restore some of the physical processes – not all the way to the historical level, but enough that that can then interact with the landscape where we’ve restored habitat, we’ve created redundant patches, large patches, connectivity, all the things and that can help us bring back the functions that we want,” she said. “The point of this is to illustrate that we can get what we want without trying to restore to historical conditions. The purpose is to regain desired ecological functions, and the approach is to restore physical processes and landscape elements.”
Ms. Grenier then touched on flows, noting that it isn’t something that their reports address much. “We refer to it without actually prescribing what the flows should be,” she said. “The State of the Estuary report in 2015 briefly talks about how much flows have changed because that’s such an important process that’s been altered over time.”
She presented a slide showing bay inflow as a percent of unimpaired flows over time. “We have records starting in the 30s and you can see that we have a lot of variability in our climate but in general, there’s a slow decline over time,” she said. “These data were analyzed by Tina Swanson at NRDC and some people take issue with that because the NRDC is an advocacy organization, so we don’t need to talk about what the colors mean as that’s an interpretation of the data, but the data are just the data. I don’t think anyone would argue with where the data points fall on this graph.”
She pointed out that the yellowy-orange bands are severe droughts. “What a severe drought used to mean in the 30s before we had a lot of water infrastructure was really different than what a severe drought means now, so there’s nothing less severe some droughts as compared to previous droughts; it’s just the change in water infrastructure and water use that’s causing that decline.”
Ms. Grenier then presented a graph illustrating actual versus unimpaired flow for 2014. “We all know that was a really tough year for water in California. The solid blue is unimpaired, and the red line is actual freshwater inflow to the Bay. That’s a really extreme change to a physical process in an estuary that’s driven by freshwater, so I think when we see this kind of data, we have to expect really extreme changes in the functions that we’re getting downstream of this. I’d say that without blaming anyone that I think sometimes when we talk about this, it seems like we’re talking ag or talking cities or we’re talking Southern California, and it’s not about that. It’s just showing the straight up data of how much transformation has been – just like we show how much marsh loss or how much flooding loss has happened. This is about half of the water being taken out of the system in 2014.”
Ms. Grenier then presented a graph of actual and unimpaired flows from 1930-2014. The driest years are the lowest 20% and those are categorized in dark red. The lighter red is represents what would have been categorized as very dry without the water infrastructure in place that we have now. “You can see that those happened and they are earlier in the century,” she said. “There were a few decades where there really weren’t any dry years or wouldn’t have been naturally, and then there are some other clumps of drought essentially here, natural drought. You can see there’s a lot more dark bars – that’s when you’re creating a very dry year because of all the water that’s being taken out of the system, the Bay is experiencing a drought. There’s not very much water coming into the Bay from the Delta.”
“It comes out to be two and a half to three times more than there would be naturally, so we’re creating a chronic artificial drought all the time,” she said. “The decades where we could have seen our system recover and our populations of wildlife recover, they can’t because they are being forced into a drought that they wouldn’t normally experience. That’s a really huge evolutionary challenge for a species that been evolved to deal with only the light red bars of drought that is now dealing with all the dark red bars of drought. It’s another way of thinking about the challenges that we’re putting into our system that we’ll have to address in restoration.”
The latest report, A Delta Renewed, offers visions for restoring desired ecological functions. The report has practical examples for restoring desired functions. For example, if the goal is to support marsh wildlife for example, there is an example of how to configure the landscape. “This gets into particular habitat types and where they might go in the Delta without trying to assign any particular parcel or landowners to what would happen, but just to get a sense of how big would the patches be, what would they be adjacent to, where in the Delta would they need to be, and how much redundancy would you be thinking about. … It’s not just natural areas, it’s integrating more ecosystem functions of that kind of natural places with the working landscape of agricultural and existing habitats that we already have.”
To get to the ecological functions, there needs to be landscape integration, as well as what to do in a particular place. “We’ve come up strategies for restoring processes because we have a very process based conceptual model, but then those strategies need to fit together. You need to fit them together in particular spaces to get that more small scale landscape configuration that can give you the functions you want.”
“We have these kinds of schematics for all of our desired functions, and we get into a lot of detail about what these process based strategies are, trying to give a lot of guidance of how this can be done, based on the science that’s out there,” she said. “We have spreads and maps that try to help people see where the opportunity areas can be, where are the right elevations, where is adjacency with the right habitats, where is public land that might be a good place to get started.”
“We try to give really specific guidance on what are the size of the patches, how should they be organized next to each other, what might you get if you restored one thing versus another, trying to say here are the options you have, here’s what the science says you might get if you make different choices,” Ms. Grenier said.
She then gave an example. “We’re still thinking about restoring marshes for wildlife, so one of our guidelines for restoring marsh based processes is marshes should be as big as possible. That’s a nice idea but what does it actually mean? What we say is here’s what you might get if you restore marshes of different sizes. At around 2 hectares, you might get a black rail, a small marsh bird, showing up. At 100 hectares, you might get an actual population of black rails that’s reached their maximum density.”
“At 500 hectares, you’re getting patch size that’s big enough that you’re getting the full tidal channel network; you get that dendritic network of channels that bring water and energy and food in and out of your marsh, so that’s the sort of process-based size that we would ideally want so that we get self-sustaining functional systems.”
Ms. Grenier pointed out that even at 500 hectares, that isn’t even coming close to the historical average patch size. “Historically, the average patch size was 4500 hectares and maximum patch size historically was 110,000 hectares, so again just to point out that we can get quite a bit without going to the incredible vast extreme wetland sizes and functions that we used to have.”
It all does come back to people, she said. “A Delta Reformed is a big blueprint, a big guide on how landscape science can help with the decisions that need to be made, but it needs to be translated into much smaller Operational Land Units (OLUs) which are the planning areas that we should be thinking about to create more local visions and involve stakeholders. That’s what DFW is doing now, and Delta Conservancy is doing these much smaller scale vision processes where our ideas for landscape science can be applied.”
“As we think about this beautiful historic landscape that we used to have and the productive and valuable landscape that we have now that’s providing a lot of water and food for our state, we can imagine that there’s an integrated future that can serve as both,” said Ms. Grenier. “Not that it will be easy, but that it is possible and hopefully there are some win-wins here. By using landscape science, hopefully we can make our restoration as effective and efficient as possible, so that we’re not doing an uncoordinated approach that’s going to end up taking a lot more land and a lot more time. If we do a thoughtful scientific coordinated approach across large scales, we can actually get what we want using the least land and water and still get the most ecological function.”
FOR MORE INFORMATION …
- For the paper, The Delta as Changing Landscapes, click here.
- For all the papers from the State of Bay Delta Science 2016, click here.
- For more information on the Delta Landscapes project from the San Francisco Estuary Institute, click here.