Why Ecological Systems are Important
An ecological system (ecosystem) is a community of living organisms and the environmental features that support them. Everything in the natural world is connected, and therefore so is everything in an ecosystem. Ecosystems have no particular size –they can be as large as the entire planet, or as small as a tree or a puddle. A terrarium is an artificial ecosystem where the water, water temperature, plants, animals, air, light and soil all work together. If there isn't enough light or water for example, the plants will die. If the plants die, the animals that depend on them will die. If the animals that depend on the plants die, any animals that depend on those animals will die, and so on. This is how ecosystems work; the parts work together to make a balanced system.
Ecosystems are essential to human existence, providing us with innumerable and invaluable services. These ecosystem services are the goods and services derived from natural and managed ecosystems upon which human welfare depends, including everything from clean water and air to food and fuel.
Unfortunately, ecosystems are in decline around the world. According to the 2005 Millennium Ecosystem Assessment, a report by the United Nations Environment Program, approximately 60 percent of the ecosystem services that support life on Earth are being degraded and/or used up faster than they can be replenished. Additionally, by 2050, the amount of per capita arable land in the US will have decreased from ~1.6 to 0.7 acres per person while simultaneously, the US population is projected to increase by 25%.
The Importance of Water
Without water there would be no life. Approximately 70% of the earth is covered in water. At birth, the human body is primarily water – nearly 80%. Because of easy access, humans tend to take water for granted and do not realize the importance of it. A person can survive about two months without food, but only a few days without water because every system in the human body depends on water to function. Here are just a few facts to explain why water is important for humans:
- The majority of the cells in our body are made up of water.
- Water is the primary component of our saliva, sweat, and tears.
- It makes up a big portion of our blood and lymph systems.
- It transports food and oxygen to different cells and carries wastes out of our bodies.
- It controls our blood pressure by balancing our bodies’ electrolytes.
- It helps the kidneys flush out toxic substances.
- It helps regulate our body temperature. It keeps us cool when the weather is hot and it insulates our bodies from cold weather.
- It serves as a shock absorber or cushion for our organs.
- It serves as a lubricant for our joints so we can move comfortably.
In addition to the specific services water provides for humans, water is also important because it determines the structure and function of the ecosystem. Cycling of all other elements in an ecosystem is also dependent upon water, as it provides the transportation and is also a solvent medium for their uptake by organisms. It is needed along with carbon dioxide in photosynthesis and has a moderating effect on the temperature of the surrounding areas because of its heat absorbing ability.
The oceans alone contain 97% of all the water on earth. Most of the remainder is frozen in the polar ice and glaciers, and less than 1% of water is present in the form of ice-free fresh water in rivers, lakes, and aquifers. However, this relatively negligible portion of the planet’s water is crucially important to all forms of terrestrial and aquatic life.
In a properly functioning ecosystem, water is used over and over again in constant movement from the earth into the atmosphere and back – this is called the water cycle. About one third of all solar energy is dissipated in driving the water cycle. Sunshine evaporates water from the oceans, lakes and streams, from the moist soil surfaces and from bodies of living organisms. Water vapor gathers in the form of clouds, which move with the winds over the earth’s surface. After cooling and condensation, water falls in the form of rain or snow. Some of the water, which falls on the land percolates through the soil until it reaches a zone of saturation. Below the zone of saturation is a solid rock through which water cannot percolate. The upper surface of this zone of saturation is known as the water table. The extra water runs off in the form of streams, which converge and joins to form rivers. Finally, water is returned to the ocean.
Climate is a very important environmental influence on ecosystems. Climate changes and the impacts of climate change affect ecosystems in a variety of ways. For example, warming could force species to migrate to higher latitudes or higher elevations where temperatures are more conducive to their survival. Likewise, as sea level rises, saltwater intrusion into a freshwater system may force some key species to relocate or die, thus removing predators or prey that were critical in the existing food chain.
Climate change not only affects ecosystems and species directly, it also interacts with other human stressors such as development. For instance, climate change may exacerbate the stress that land development places on fragile coastal areas. Additionally, recently logged forested areas may become vulnerable to erosion if climate change leads to increases in heavy rainstorms. A 2007 global analysis of the potential effect of climate change on river basins showed that many rivers impacted by dams or extensive development will require significant management interventions to protect ecosystems and people. The projections from this study indicate that every populated basin in the world will experience changes in river discharge. Some are expected to have large increases in flood flows, while other basins will experience water stress to the point that there is not enough water to meet human needs. For example, the paper projects that by the 2050's, mean annual river discharge is expected to increase by about 20 percent in the Potomac and Hudson River basins but to decrease by about 20 percent in Oregon's Klamath River and California's Sacramento River. For more information, see http://www.sciencedaily.com/releases/2007/10/071012105820.htm
For most species, the climate where they live or spend part of the year influences key stages of their annual life cycle, such as migration, blooming, and mating. As the climate has warmed in recent decades, the timing of these events has changed in some parts of the country. Some examples include:
- Warmer springs have led to earlier nesting for 28 migratory bird species on the East Coast of the United States.
- Northeastern birds that winter in the southern United States are returning north in the spring 13 days earlier than they did in the early 20th century.
- In a California study, 16 out of 23 butterfly species shifted their migration timing and arrived earlier.
Changes like these can lead to mismatches in the timing of migration, breeding, and food availability. When migrants arrive at a location before or after food sources are present, growth and survival are reduced.
The impact of climate change on a particular species can also ripple through a food web and affect a wide range of other organisms. For example, declines in the duration and extent of sea ice in the Arctic leads to declines in the abundance of ice algae, which thrive in nutrient-rich pockets in the ice. These algae are eaten by zooplankton, which are in turn eaten by Arctic cod, an important food source for many marine mammals, including seals. Seals are eaten by polar bears. Therefore, declines in ice algae can contribute to declines in polar bear populations.
Along with habitat destruction and pollution, climate change is one of the important stressors that can contribute to species extinction. The Intergovernmental Panel on Climate Change estimates that 20-30% of the plant and animal species evaluated so far in climate change studies are at risk of extinction if temperatures reach levels projected to occur by the end of this century. Projected rates of species extinctions are 10 times greater than recently observed global average rates and 10,000 times greater than rates observed in the distant past (as recorded in fossils). Examples of species that are particularly climate sensitive and could be at risk of significant losses include animals that are adapted to mountain environments, such as the pika (currently present above 11,000ft in New Mexico), animals that are dependent on sea ice habitats, such as ringed seals, and cold-water fish, such as salmon in the Pacific Northwest.
Climate change is likely to alter ecosystems and the ability of ecosystems to react to stress. While plants, animals, and microorganisms have been adapting to environmental changes for millions of years, the pace of climate changes happening now will require species to adapt more quickly. Climate change impacts on ecosystems may include salt water intrusion, habitat shifts, increased invasive species survival, enhanced competition for limited resources, and amplification of existing stressors, such as habitat fragmentation and pollution.
Climate Change and The Rio Grande
The Rio Grande Basin is located in the southwestern United States and provides water for irrigation, households, the environment and recreational uses in Colorado, New Mexico and Texas as well as Mexico (see map below). The Bureau of Reclamation has two major projects within the Rio Grande basin, which irrigate approximately 250,000 acres and provide critical water and power for industry and communities including Albuquerque and Las Cruces in New Mexico, El Paso, Texas and Ciudad Juarez in Mexico. The Rio Grande Basin supports critical habitat for the Rio Grande silvery minnow and the southwestern willow flycatcher, both of which are designated as endangered under the Endangered Species Act.
The total river length is 1,896 miles, and drains a total of approximately 182,200 square miles. Basin topography varies from the mountains and gorges of the headwaters to the Bosque and high desert of central New Mexico, to deserts and subtropical terrain along the boundary between Texas and Mexico. Most of the basin is arid or semi-arid, generally receiving less than 10 inches of precipitation per year. In contrast, some of the high mountain headwater areas receive on average over 40 inches of precipitation per year. Most of the total annual flow in the Rio Grande basin results, ultimately, from runoff from mountain snowmelt.
The river is heavily utilized, and the river channel size is significantly smaller in the Lower Rio Grande than it is in the Upper Rio Grande. In recent years, intermittent and low flows have occurred in the lower reaches, and river flows do not reach the Gulf of Mexico every year. Along with water quantity, other important issues in the Rio Grande basin include threatened and endangered species and water quality.
In 2011, the Bureau of Reclamation released the Reclamation Climate Change and Water 2011, Section 6 - Basin Report: Rio Grande. The full report may be read online at www.usbr.gov/climate. A fact sheet is also available at www.usbr.gov/climate/SECURE/docs/riograndebasinfactsheet.pdf, which summarizes the findings.
Future changes in climate and hydrology they predict include:
- Climate projections suggest that temperatures throughout the Rio Grande are projected to increase by roughly 5–6 °F during the 21st century.
- The projections also suggest that annual precipitation in the Rio Grande Basin will remain quite variable over the next century with a decrease of from 2.3 to 2.5% by 2050.
- Mean annual runoff is projected to decrease by from 7.3 to 14.4% by 2050.
- Moisture falling as rain instead of snow at lower elevations will increase the wintertime runoff and decrease runoff during the summer.
Future Impacts for Water and Environmental Resources include:
- Spring and early summer runoff decreases may translate into water supply reductions for meeting irrigation demands, adversely impacting hydropower operations and increasing wintertime flood control challenges.
- Warmer conditions might result in increased stress on fish such as the silvery minnow, increased water demands for instream flows for ecosystems and increased invasive species infestations.
- The upper Rio Grande Basin is heavily reliant on ground water for municipal and rural uses. Warmer conditions might increase evaporation and decrease runoff, which will likely result in less natural groundwater recharge, resulting in even lower ground water levels.
Streamflow in the Rio Grande basin varies significantly from month to month as well as from year to year. The majority of the annual streamflow in the?Rio Grande basin comes in spring and early summer as a result of snowmelt. Streamflow is lowest in late summer and fall; however, flows can be temporarily augmented by runoff from localized monsoon precipitation events. The projections from the Bureau of Reclamation Climate Change and Water Report also suggest that annual precipitation in the Rio Grande basin will remain quite variable over the next century. Temperature and precipitation changes are expected to affect hydrology in various ways including snowpack development. Warming is expected to diminish the accumulation of snow during the cool season (i.e., late autumn through early spring) and the availability of snowmelt to sustain runoff to the Upper Rio Grande from late spring through early autumn. Snowpack decreases are expected to be more substantial over the portions of the basin where baseline cool season temperatures are generally closer to freezing thresholds and more sensitive to projected warming--this is particularly the case for the lower lying areas of the basin.
The report goes on to state that changes in climate and snowpack within the Upper Rio Grande basin will change the availability of natural water supplies. These changes may be due to annual runoff, and also changes in runoff seasonality. For example, warming without precipitation change would lead to increased evapotranspiration from the watershed and decreased annual runoff. Precipitation increases or decreases (either as rainfall or snowfall) would offset or amplify the effect. Their results suggest that annual runoff changes are generally consistent but do vary slightly by location in the Upper Rio Grande basin depending on baseline climate and the projected temperature and precipitation changes. For example, annual runoff reductions in the Rio Chama at Abiqiu, draining the northwestern reaches of the basin, are projected to be somewhat less than reductions found at river locations draining the northern and eastern portions of the basin. However, at all locations, decade-mean annual runoff is projected to steadily decline through the 21st century, responding to both slight decreases in precipitation and warming over the region.
The seasonality of runoff is also projected to change in the Upper Rio Grande. Warming would be expected to lead to more rainfall and runoff, rather than snowpack accumulation, during the winter. Conceptually, this change would lead to increases in the December–March runoff and decreases in the April–July runoff.
Throughout the country, people are beginning to recognize the important connections between climate change and water availability. These potential challenges are particularly troublesome for residents of the southwest, where the climate is already highly variable and droughts are common. For more information, please see our Climate Change Resources to the right.