[MUSIC] I'm Erika Zavaleta and this is Ecosystems of California. California's rivers drain a huge variety of water sheds all over the state from thousands to tens of square kilometers. And an echo systems that range from grasslands to deserts, the Redwood Forests of the coast and the Montane Forest of the Sierra. Many of California's rivers have been severely altered through the building of dams and the diversion and transport of water that characterizes so much of this state. And they've also been affected over the years by mining, introduced species, and changes in the land cover and the watersheds that they drain. Nevertheless, particularly in a state with annual summer droughts and with many areas of low precipitation. California's rivers support tremendous biodiversity. Both for migrating birds and wide ranging terrestrial animals as well as for residence species. I'm at the south fork of the American River. Which changed the course of the world's history when in 1848, California's gold was first discovered on this river. The south fork of the American River drains a huge part of the Western Sierra immediately west of Lake Tahoe and in the part that I'm standing, where the river is free flowing,. It's hydrography or its annual fluctuations in flow levels vary with precipitation events and snow melts, and that variation causes flood events and high flow events as well as periods of low flow. Those high flow periods are important because they scour the bottom, cleaning out sediment and creating great fish habitat at the bottom by keeping the gravel and cobble clear. They also scour the banks of the river which maintains habitat for flood adapted riparian vegetation like some of what you see behind me in the willows. Conversely, the riparian vegetation that's maintained along rivers, like the the south fork of the American, help provide habitat, both for terrestrial wildlife that come and depend on the river corridor for water, and for the greater structural diversity of the habitat here, and in the water. The aquatic organisms in many of California's rivers depend on shading from riparian vegetation to keep water temperatures cool. And also depend on inputs of litter and detritus to maintain and support the food web inside the river. Finally, coarse woody debris or just big pieces of wood that come down the river with floods or that fall in to the river from the riparian corridor, are really important sources of structural habitat in the river. And so, in a free flowing river, in all of these ways, the variation in flows helps maintain the biological diversity and integrity of the river and ecosystem. So this is cool, these little bundles of pebbles are caddisfly larval cases. And caddisfly larvae will build these out of little pebbles on the bottoms of rocks in the water. They're usually at the bottom of the river so right now we're about a meter higher than the surface of the river. These must be left here from when the river was running quite a bit higher. And caddisfly larvae are one of many benthic macroinvertebrates that form the base of the consumer food web and provide food for fishes. And then, when they mature, the adult form is a winged organism. So they will emerge from the surface of the river and fly out. And then they are potentially providing food for terrestrial animals like birds. [SOUND] I'm standing in front of the Folsom Dam in the Sacramento of California. Above the dam is the Folsom Reservoir into which not only the south fork of the America but also the middle and the north forks flow. Folsom Reservoir is stocked with introduced fishes including sunfish and bass, and so it's popular with recreational fishers. Below the dam, the American River waters are released fairly evenly without a lot of variation in ideograph, and so those waters flow from here through the city of Sacramento where they join with the Sacramento River. From the Sacramento River, then those waters flow on into the Sacramento Bay Delta. Now Sacramento is the major river that drains the northern half of the Central Valley. And when it merges with the San Joaquin River at the delta, it becomes the largest part of a system of water diversion and transfer in California. But also a large part of what was once a vast inland sea. We're now 40 kilometers or about 25 miles south of Sacramento, in the delta of the Sacramento and San Joaquin Rivers. The delta is an enormous area, 700 square miles or 1,800 square kilometers and it made up of a series of almost 60 islands and series of levees that were built over the last several decades in order to drain what were originally a vast wetland for agriculture. In the 1770's when explorer's arrived here, the delta consisted of 300,000 hectares, an area the size of Rhode Island, of Brakish water, vast England Estuary. Overtime as that was drained for agriculture and Lexis were built. Carbon dioxide stored in the peat soils underneath that water was off gassed and as that CO2 left, the lands subsided considerably. As a result, this region is referred to the Holland of California because much of it is on the order of 5 to 8 meters below sea level. And so, those levies now provide really critical protection against flooding from the ocean side, which would bring salty water into the region, and destroy a lot of these farms. The delta is still home to almost 750 species of wildlife, and it supports a variety of recreational fishers and commerce, because boats come up into the delta from the San Francisco and Sassoon bays to deliver goods as far up as the port of Sacramento. So we haven't reached the very end of the American River in a sense because although it's flowed into the Sacramento above us, and the Sacramento and San Joaquin have joined here to form the Delta. Ultimately, the waters here, about 25% of them will now be transported elsewhere in California, where they're used by on the order of 23 million people now. The rest of the waters head out eventually to the San Francisco Bay, the Sassoon Bay, and eventually out the Golden Gate to the ocean. Over the decades, the competing uses of water use on the one hand and wildlife habitat in the other have made it difficult for the delta to meet either of those needs very well. Some species like the delta smelt which is now federally listed have triggered protections for some of the water in the delta requiring more of it to be left here and to be allowed to go out to sea but other problems persist. There are a lot of invasive species here and water quality is a constant problem. So the delta, particularly as climate change reduces water supplies in California, is going to be a difficult management challenge for many decades to come. Not all rivers are as extensive or as altered as the American Here on the Big Sierra coast, steep mountains that drop almost directly into the ocean support a number of small creeks, each of them draining a small watershed with relatively little land use or land cover change in it. I am on Devil's Creek in the Big Creek Landos Hill Reserve, part of the University of California natural reserve system. And here on Big Creek two creeks, Devils Creek right here and Big Creek which it joins lower down, drain watersheds that have experienced essentially no land cover change in several decades. So because of that they're an opportunity to see how a relatively pristine and unaltered watershed and river ecosystem function. Native fishes, steel head which are anagramous, begin their lives here in Devils Inn Big Creek. They hatch here, go down to the ocean to spend most of their adult lives and then return here to spawn. Those steel heads sit atop a trophic web that in these highest reaches of these creeks high in the watershed starts with inputs of primary production from land. So here in these highest reaches of these watersheds, the primary source of energy for the consumer web in a river or a stream is leaf litter and other inputs from the surrounding land area. Because of that, the macroinvertebrates and other consumers in the stream tend to focus on strategies like shredding leaf litter to obtain their food. But as we'll see as we go lower down into the water shed, the source of primary production shifts towards more primary production within the stream by algae that can take advantage of sunlight that's more available as the stream widens. So we'll see this shift occurring from primarily alofonos sources of primary production. Alofonos meaning outside of the system, to autofonos sources of primary production or occurring within the system. [NOISE] As the creek widens downstream, sunlight supports increased primary productivity within the stream by algae. And this is accompanied by a shift in the consumers in the macroinvertebrates community towards species like caddisflys that specialize in grazing the algae off of surfaces like rocks. Generally, macroinverterbrate communities in streams are excellent indicators of the state of a stream. Because there will be shifts in the relative abundances of different foraging strategies. Shredders, grazers and other groups like collectors and predators, as well as shifts taxonomically, in response to. Stresses like pollution, grazing, and logging and disturbances like wildfires and floods. Small fishes consume this whole range of macaroon vertebrates in the stream as well as terrestrial insects and other invertebrates that fall into the water. In general, California's freshwater fishes have been heavily impacted by human activity, and about a quarter of the state's fresh water fish species are in imminent danger of extinction. Here in the protected streams of Big Creek Reserve are followed closely by National Marine Fishery Service scientists. Evolutionarily distinct population segments of steel head continue to thrive not only through seasonal fluctuations and droughts. Things like El Nino cycles and events like wildfires but also so far through climate change. And that's in large part because not only the riparian vegetation around the creek, but also the entire water shed remain relatively undisturbed and intact. [MUSIC]
