What factors change ecosystemPresentation Transcript
How have ecosystems changed? Freshwater ecosystem:– Modified by the creation of dams and the withdrawal of water for human use, whichhave changed the flow of many large river systems. reducing sediment flows, the main source of nutrient for estuary ecosystems. Terrestrial ecosystems: More than half of the original area of many types of grasslands and forest hasbeen converted into farmland. The only types of land ecosystems which havebeen changed relatively little are tundra and boreal forests, but climate changehas begun to affect them.. Globally, the transformation of ecosystem into farmland has begun to slowdown. Opportunities for further expansion of farmland are diminishing in manyregions of the world because most of the suitable land has already beenconverted. Increased agricultural productivity is also reducing the need for more farmland.Moreover, in temperate regions some cropland areas are now reconverted intoforest or taken out of production.
Do environmental cycles affected? Hydrological Cycle– Water withdrawals from rivers and lakes for irrigation, urban uses, and industrialapplications doubled between 1960 and 2000. Carbon Cycle– In the last two and a half centuries, the concentration of carbon dioxide in theatmosphere has increased by one third. Land ecosystems were a net source ofcarbon dioxide during the 19th and early 20th century and became a net carbon sinksometime around the middle of the last century. This reversal is due to increases inplant growth system-e.g. new forest management and agricultural practices. Nitrogen Cycle– The total amount of nitrogen made available to organisms by human activitiesincreased nine-fold between 1890 and 1990, especially since 1950 because of theuse of synthetic fertilizers. Human activities are now responsible for as much nitrogenmade available as all natural sources combined. Phosphorus cycle– The use of phosphorus fertilizers and the rate of phosphorus accumulation inagricultural soils nearly tripled between 1960 and 1990, but has declined somewhatsince. The flow of phosphorus into the oceans is now three times the natural flow
Are biodiversities also changed? The distribution of species on Earth isbecoming more homogeneous. Majority of species have faced a decline inthe size of their population, in theirgeographical spread, or both.. Species extinction is a natural part of Earth’shistory. The range of genetic differences withinspecies has declined, particularly for cropsand livestock. In cultivated ecosystem, intensification ofagriculture and the lesser use of traditionallocal species in favor of fewer modernvarieties have reduced the genetic diversityof domesticated plants and animals. The permanent loss of genetic diversity hasbeen partially prevented by maintaining seedbanks.
Are Ecosystem Services and TheirUses also Changed? Approximately 60% (15 out of 24) of the ecosystemservices (including 70% of regulating and culturalservices) are being degraded or used unsustainably The quantity of provisioning ecosystem services suchas food, water, and timber used by humans increasedrapidly. Provisioning services are being used atunsustainable rates. Humans have substantially altered regulating servicessuch as disease and climate regulation by modifyingthe ecosystem providing the service and, in the case ofwaste processing services, by exceeding thecapabilities of ecosystems to provide the service Although the use of cultural services has continued togrow, the capability of ecosystems to provide culturalbenefits has been significantly diminished in the pastcentury The modification of an ecosystem to alter oneecosystem service (to increase food or timberproduction, for instance) generally results in changesto other ecosystem services as well
Factors causing ecosystemchanges
What are the most critical factorscausing ecosystem changes? Natural or human-inducedfactors that directly or indirectlycause a change in anecosystem. Drivers affect ecosystemservices and human well-beingat different spatial and temporalscales, which makes both theirassessment and theirmanagement complex
What is a "driver" and how does itaffect ecosystems? A direct driver– Habitat change, explicitly influences ecosystem processes. An indirect driver– Change in human population, operates more diffusely, by altering one or moredirect drivers. Range of driver– From local to global and from immediate to long-term, which makes both theirassessment and management complex.– Climate change may operate on a global or large regional scale;– Political change may operate at the scale of a nation or a municipal district. Socio-– Cultural change typically occurs slowly, on a time scale of decades,– Economic changes tend to occur more rapidly. As a result of this spatial and temporal dependence of drivers, the forces thatappear to be most significant at a particular location and time may not be themost significant over larger, or smaller, regions or time scales.
What are the indirect drivers and howare they changing? Population change:– Population growth and migration. Change in Economic activity:– As per capita income grows, demand for many ecosystem services increases and thestructure of consumption also changes. The share of income devoted to food, forexample, decreases in favor of industrial goods and services. Socio-Political factors:– Include decision-making processes and the extent of public participation in them. Thetrend toward democratic institutions over the past 50 years has helped empower localcommunities. There has also been an increase in multilateral environmentalagreements. Cultural and Religious factors:– Culture can be defined as the values, beliefs, and norms that a group of people share.It conditions individuals’ perceptions of the world, and suggests courses of actionwhich can have important impacts on other drivers such as consumption behavior. Science and Technology:– Much of the increase in agricultural output over the past 40 years has come from anincrease in yields per hectare rather than an expansion of area.
Changes in the impacts of indirectdrivers Consumption of ecosystem services isslowly being decoupled fromeconomic growth. Global trade magnifies the effect ofgovernance, regulations, andmanagement practices on ecosystemsand their services, enhancing goodpractices but worsening the damagecaused by poor practices Urban demographic and economicgrowth has been increasing pressureson ecosystems globally, but affluentrural and suburban living often placeseven more pressure on ecosystems
What are the direct drivers of changesin ecosystem services? For terrestrial ecosystems, in the past 50 years, in the aggregate,have been land cover change (in particular, conversion tocropland) and the application of new technologies (which havecontributed significantly to the increased supply of services suchas food, timber, and fiber) Both land cover changes and the management practices andtechnologies used on lands may cause major changes inecosystem services For marine ecosystem and their services, the most importantdirect driver of change in the past 50 years, in the aggregate, hasbeen fishing For freshwater ecosystems and their services, depending on theregion, the most important direct drivers of change in the past 50years include modification of water regime, invasive species, andpollution, particularly high levels of nutriewnt loading. Coastal ecosystem are affected by multiple direct drivers
Most important direct drivers Over the past four decades,excessive nutrient loading hasemerged as one of the mostimportant direct drivers ofecosystem change in terrestrial,freshwater, and marineecosystems. Climate change in the pastcentury has already had ameasurable impact onecosystems