How have environmental cycles changed? The capacity of ecosystems to provide benefits to humans, that is to provide ecosystem services, derives from environmental cycles of water, nitrogen, carbon, and phosphorus. These processes have in some cases been significantly modified by human activity. Changes have been more rapid in the second half of the 20th century than at any other time in recorded human history. Water cycle: Water withdrawals from rivers and lakes for irrigation, urban uses, and industrial applications doubled between 1 960 and 2000. Globally, humans use slightly more than 10% of the available renewable rosewater supply.
However, in some regions such as North Africa, groundwater is withdrawn at a faster pace than it is renewed. Carbon cycle: In the last two and a half centuries, the concentration of carbon dioxide in the atmosphere has increased by one third. Land ecosystems were a net source of carbon dioxide during the 1 9th and early 20th century and became a net carbon sink sometime around the middle of the last century. This reversal is due to increases in plant growth brought about by, for example, new forest management and agricultural practices. Nitrogen cycle: The total amount of trigger made available to organisms by human activities increased nine-fold between 1890 and 1 990, especially since 1950 because of the use of synthetic fertilizers.
Human activities are now responsible for as much nitrogen made available as all natural sources combined. Phosphorus cycle: The use of phosphorus fertilizers and the rate of phosphorus accumulation in agricultural soils nearly tripled between 1960 and 1 990, but has declined somewhat since. The flow of phosphorus into the oceans is now three times the natural flow. This study is focused on stream and landscape modifications and their effects n interaction between two predatory fish: brown trout and walleye. Both species in the Au Sable River system make extensive long-range movements.
Brown trout in both the Mainstream and South Branch regularly moved 300-3,000 m each night during the summer. The extent of these movements was correlated to gradient. A third study in Mainstream between MIM and Alcoa Pond indicated that brown trout there showed much lower daily movements than in upstream reaches. Brown trout remained within 25 km of MIM Dam (out of a possible 50 km) and during summer remained relatively inactive. Their low rates of activity were correlated again to gradient, but also to presence of dams, which may have interfered with longer upstream movement.
Walleye commonly used the same stretch of river as brown trout, as well as Alcoa pond on the downstream end. They regularly moved between the pond and river system, and passed over the lower 25 km. The upper reach of this study area was also heavily influenced by MIM Pond, which combined with local development to reduce large woody debris in the river, to increase water temperature, and to decrease temperature flux. Interactions in this dammed reach include predation by walleye on small rowan trout. This interaction may result in a lack of recruitment for brown trout between MIM and Alcoa Pond.
Dams and impoundments on the Usable River increase walleye populations and interactions between walleye and brown trout, both to the detriment of the brown trout fishery. They also largely influence stream conditions and aquatic communities within the study reaches. Healthy ecosystems are a fundamental requirement for sustainable development and biodiversity conservation. Biological resources support human livelihoods, and make it possible to adapt to changing needs and environmental conditions. Many sectors of national economies also depend on the diversity of ecosystems and the functions and services they perform or protect.
However, present trends of economic development, supported by inappropriate financial incentives, typically undervalue the ecosystem processes and services leading to the Overexploitation of valuable resources worldwide. As a result, species are becoming extinct at an alarming rate and the degradation of many ecosystems, biomass and habitats are leading to unprecedented social strife. Most of this has taken place in the developing world and in countries in transition The irreversibility of species extinction, ND the loss of genes and transformation of ecosystems through habitat degradation and overexploitation, all compromise options for present and future generations. It is therefore not possible to achieve a sustainable pattern of development without an effective strategy for ecosystem conservation and restoration. In recognition of this, development agencies need to integrate the conservation of biodiversity and ecosystems in development actions, and to implement ecologically effective, socially beneficial and economically viable ecosystem management practices in forests, wetlands, Savannah, arid and semi-arid rangelands, coastal and urine areas, mountains and agro-ecosystems.
Traditional approaches to biodiversity conservation have largely focused on conserving species and establishing various forms of protected areas. However, biodiversity will not be conserved effectively in protected areas alone. The existing global network of protected areas is too small and, under prevailing social and economic conditions, any major expansion of this network seems unlikely. Many existing protected areas are under threat and, even where significant areas have been placed in protected areas, prevailing development patterns are creating barriers to species interaction and migration. The fragmentation of natural habitats has reduced the long-term viability of protected areas by making species more vulnerable to genetic erosion and to the impacts Of climate change.
Thus, it has been recognized that, in addition to the establishment of protected areas, the future of much of the biosphere will depend on managing large areas using an integrated approach that recognizes human populations as having a keen interest in ensuring the continuing productivity of the ecosystems within which they live. Such an approach will have to meet local needs, maintain or restore ecosystem integrity and conserve biodiversity, simultaneously. Burch State Natural Area is a 728-acre natural area located in Germantown and Shelby County and is a part of a larger 6,000-acre county park (http://BMW. Selenographers. Org/esp./front).
The natural area is a remnant of historic river meanders, bald cypress-water tupelo swamps, bottommost hardwood forests, and open river channel habitat. Unfortunately, much of this ecosystem has been significantly altered as a result of change in hydrology and the invasion of common privet, an invasive exotic pest plant. Luscious E. Burch Natural Area offers passive recreation activities such as day hiking, bird watching, and wildlife viewing within the metropolitan Memphis area. The natural area is a relatively large unfrequented forest that follows the banks of the Wolf River.
It provides a refuge for forest dwelling birds, mammals, reptiles, and amphibians within an urbanize environment. Luscious E. Burch State Natural Area is a place where impacts on the resource can be interpreted and used as an educational tool to demonstrate the ecological effects of river centralization (straightening of the river channel) ND the impacts of invasive exotic pest plants. This outdoor living classroom is reacting to the change in environmental conditions since it was channeled. Common privet is native to Asia and has been widely used as hedges in urban landscaping.
It has spread throughout the understood at Luscious E. Burch and has displaced many native species. Its impact is indicative of a problem facing all urban natural areas where adjacent landowners introduce invasive exotic pest plants. These landscaping practices create the seed source from which invasive exotics are distributed into natural areas by animals, wind, or water. Privet has invaded at Luscious E.
Burch since drier site conditions were created by the centralization of the Wolf River. This invasion often occurs when a natural ecological disturbance regime has been altered or where the native landscape has been severely changed by development. Historically, the site was bottommost forest and a part of the Wolf River floodplain. This is evident by the occurrence of large cypress trees that are periodically encountered in relatively dry habitats. The state listed Copper iris (Iris vulva) is found in some existing low wet areas in the natural area.