Konsep Ekosistem




Download 1.95 Mb.
TitleKonsep Ekosistem
Page2/14
Date conversion13.09.2012
Size1.95 Mb.
TypeDocuments
Sourcehttp://marno.lecture.ub.ac.id/files/2012/01/KONSDEP-DASAR-AGROEKOSISTEM.doc
Related:
1   2   3   4   5   6   7   8   9   ...   14
^

Indikator kesehatan agro-ecosystem


What is the route by which a metaphor or concept can be applied to something so that researchers or practitioners can use in the field? For example, there is the interest in indicators, or measurable properties which indicate the health of an agro-ecosystem. For indicators, which represent only one element of any analysis, three distinct approaches have been tried.

Holistik


This approach, of which several versions have been proposed, aims to define a set of very generic 'criteria', essentially from first principles, which will be applicable to all dimensions. Thus, we get such 'holistic indicators' as integrity, efficiency, resilience, effectiveness, response capability, balance, richness, transformation ability, self-regulatory capacity, flexibility, stability, and so on. A particular appeal of this approach is the expectation that the selected criteria will lead to measurable equivalent indicators on each of the dimensions.




A conceptual framework for agro-ecosystem health.

Sumber: http://www.ilri.org/InfoServ/Webpub/fulldocs/Aesh/Concepts.htm ..... diunduh 29/6/2011

^

Terintegrasi = Disaggregated


In this approach, the indicators of the various dimensions of agro-ecosystem health are supplied by scientists and practitioners in each of the disciplines involved. Indicators developed via this route tend to reflect the variables which are conventionally analysed in the various disciplines. Thus, economists provide indicators such as gross margins, benefit /cost ratios, or net income. Sociologists will list measures of household and community structure, power relations, equity, gender roles, and so on. From the human health and nutrition fields come indicators of morbidity, longevity, other physiological features and measures of nutritional status or functionality. From the geophysical and biological sciences come equally long lists of ecosystem variables which have been of theoretical interest or have been used before. This approach certainly generates an ample smorgasbord of indicators. The weaknesses of this approach are that the lists are impractically long, there are no established principles for selecting from among the many possibilities (they may all be 'scientifically valid'), and they often are not readily understood by the people in the agro-ecosystems.
^

Berbasis Komunitas = Community-based


The essence of this approach (also called stakeholder-derived) is that the indicators are identified with the active participation of the people who live in the agro-ecosystem. A variety of methods are available for this kind of participatory approach, in which the researchers necessarily play at least a facilitatory role, but where the indicators are certainly meaningful to local people as well as to the analysts. These include a practical and efficient way of selecting key indicators, allowing researchers to learn about communities' priorities and alternative measurements (sometimes supplied directly by residents), and promotion of people's involvement in (and 'ownership of') both analysis of agro-ecosystems and any management initiatives to improve their health.

^ Bagaimana Ekosistem Sehat menjadi Patologis


Stress from human activity is a major factor in transforming healthy ecosystems to sick ecosystems. Chronic stress from human activity differs from natural disturbances. Natural disturbances (fires, floods, periodic insect infestations) are part of the dynamics of most ecosystems. These processes help to "reset" ecosystems by recycling nutrients and clearing space for recolonization by biota that may be better adapted to changing environments. Thus, natural perturbations help keep ecosystems healthy. In contrast, chronic and acute stress on ecosystems resulting from human activity (e.g., construction of large dams, release of nutrients and toxic substances into the air, water, and land) generally results in long-term ecological dysfunction.


Lima sumber utama cekaman (stress) antropogenik (akibat dari kegiatan manusia) terhadap ekosistem, yaitu: rekayasa struktur fisik, panen berlebihan, limbah residual, masuknya spesies eksotik, dan perubahan global.


^ Rekayasa Struktur Fisik

Aktivitas-aktivitas seperti drainage rawa-rawa, pengerukan dasar danau, pembendungan sungai, dan pembangunan jalan raya, berarti proses fragmentasi bentang lahan dan mengubah serta merusak habitat-habitat kritis. Aktivitas-aktivitas ini juga mengganggu siklus hara dan menyebabkan hilangnya biodiversitas.


^ Panen berlebihan

Overexploitation is commonplace when it comes to harvesting of wildlife, fisheries, and forests. Over long periods of time, stocks of preferred species are reduced. For example, the giant redwoods that once thrived along the California coast now exist only in remnant patches because of overharvesting. When dominant species like the giant redwoods (arguably the world's tallest tree—one specimen was recorded at 110 meters tall with a circumference of 13.4 meters) are lost, the entire ecosystem becomes transformed. Overharvesting often results in reduced biodiversity of endemic species, while facilitating the invasion of opportunistic species.


^ Limbah / Residu.

Discharges from municipal, industrial, and agricultural sources into the air, water, and land have severely compromised many of the earth's ecosystems. The effects are particularly apparent in aquatic ecosystems. In some lakes that lack a natural buffering capacity, acid precipitation has eliminated most of the fish and other organisms. While the visual effect appears beneficial (water clarity goes up) the impact on ecosystem health is devastating. Systems that once contained a variety of organisms and were highly productive (biologically) become devoid of most lifeforms except for a few acid-tolerant bacteria and sediment-dwelling organisms.


^ Introduksi Spesies Eksotik

The spread of exotics has become a problem in almost every ecosystem of the world. Transporting species from their native habitat to entirely new ecosystems can wreck havoc, as the new environments are often without natural checks and balances for the new species. In the Great Lakes Basin, the accidental introduction of two small pelagic fishes, the alewife and the rainbow smelt, combined with the simultaneous overharvesting of natural predators, such as the lake trout, led to a significant decline in native fish species.

The introduction of the sea lamprey, an eel-like predacious fish that attacks larger fish, into Lake Erie and the upper Great Lakes further destabilized the native fish community. The sea lamprey contributed to the demise of the deepwater benthic fish community by preying on lake trout, whitefish, and burbot. This contributed to a shift in the fish community from one that had been dominated by large benthics to one dominated by small pelagics (fish found in the upper layers of the lake profile). This shift from bottom-dwelling fish (benthic) to surface-dwelling fish (pelagic) has now been partially reversed by yet another accidental introduction of an exotic: the zebra mussel. As the zebra mussel is a highly efficient filter of both phtyoplankton and zooplankton, its presence has reduced the available food in the surface waters for pelagic fish. However, while the benthic fish community has gained back its dominance, the preferred benthic fish species have not yet recovered owing to the degree of initial degradation. Overall, the increasing dominance by exotics not only altered the ecology, but also reduced significantly the commercial value of the fisheries.


^ Perubahan Global

Rapid climate change (or climate warming) is an emerging potential global stress on all of the earth's ecosystems. In evolutionary time, there have of course been large fluctuations in climate. However, for the most part these fluctuations have occurred gradually over long periods of time. Rapid climate change is an entirely different matter. By altering both averages and extremes in precipitation, temperature, and storm events, and by destabilizing the El Niño Southern Oscillation (ENSO), which controls weather patterns over much of the southern Pacific region, many ecosystem processes can become significantly altered. Excessive periods of drought or unusually heavy rains and flooding will exceed the tolerance for many species, thus changing the biotic composition. Flooding and unusually high winds contribute to soil erosion, and at the same time add to nutrient load in rivers and coastal waters.

These anthropogenic stresses have compromised ecosystem function in most regions of the world, resulting in ecosystem distress syndrome (EDS). EDS is characterized by a group of signs, including abnormalities in nutrient cycling, productivity, species diversity and richness, biotic structure, disease prevalence, soil fertility, and so on. The consequences of these changes for human health are not inconsiderable. Impoverished biotic communities are natural harbors for pathogens that affect humans and other species.


^ Kesehatan Ekosistem dan Kesehatan Manusia

An important aspect of ecosystem degradation is the associated increased risk to human health. Traditionally, the concern has been with contaminants, particularly industrial chemicals that can have adverse impacts on human development, neurological functions, reproductive functions, and that appear to be causative agents in a variety of carcinomas. In addition to these serious environmental concerns (where the remedies are often technological, including engineering solutions to reduce the release of contaminants), there are a large number of other risks to human health stemming from ecological imbalance.

Ecosystem distress syndrome results in the loss of valued ecosystem services, including flood control, water quality, air quality, fish and wildlife diversity, and recreation. One of the major signs of EDS is increased disease incidence, both in humans and other species. Human population health should thus be viewed within an ecological context as an expression of the integrity and health of the life-supporting capacity of the environment. Ecological imbalances triggered by global climate change and other causes are responsible for increased human health risks.


^ Hubungan keterkaitan antara jasa-jasa ekosistem, aspek kesejahteraan manusia dan Kesehatan Manusia




Sumber: http://www.mindfully.org/Heritage/2005/Ecosystem-Degradation-Threats9dec05.htm ….. diunduh 1/7/2011


Tekanan-tekanan terhadap ekosistem dapat mengakibatkan gangguan yang tidak terduga pada aspek kesehatan masa mendatang. Beberapa masalah yang sangat serius adalah

(Sumber: http://www.who.int/mediacentre/news/releases/2005/pr67/en/index.html:)

  • Gizi dan Nutrisi: Degradasi ekosistem perikanan dan ekosistem pertanian merupakan factor-faktor penyebab mal-nutrisi yang dialami 800 juta manusia di seluruh dunia. Ada banyak penduduk lainnya yang mengalami defisiensi kronis mikro-nutrient.

  • Air minum yang aman: Water-associated infectious diseases claim 3.2 million lives, approximately 6% of all deaths globally. Over one billion people lack access to safe water supplies, while 2.6 billion lack adequate sanitation, and related problems of water scarcity are increasing, partly due to ecosystem depletion and contamination.

  • Ketergantungan pada bahan bakar padat: Sekitar 3% dari beban gangguan penyakit global disebabkan oleh pencemaran udara “indoor”, penyebab utama penyakit pernafasan. Banyak penduduk dunia menggunakan bahan bakar padat untuk memasak makanan dan menghangatkan ruangan, merupakan penyebab utama penggundulan hutan.



^ Perubahan Iklim dan Vektor Penyakit


The global infectious disease burden is on the order of several hundred million cases per year. Many vector-borne diseases are climate sensitive. Malaria, dengue fever, hantavirus pulmonary syndrome, and various forms of viral encephalitis are all in this category. All these diseases are the result of arthropod-borne viruses (arboviruses) which are transmitted to humans as a result of bites from blood-sucking arthropods.

Global climate change—particularly as it impacts both temperatures and precipitation—is highly correlated with the prevalence of vector-borne diseases. For example, viruses carried by mosquitoes, ticks, and other blood-sucking arthropods generally have increased transmission rates with rising temperatures. St. Louis encephalitis (SLE) serves as an example. The mosquito Culex tarsalis carries this virus. The percentage of bites that results in transmission of SLE is dependent on temperature, with greater transmission at higher temperatures.

The temperature dependence of vector-borne diseases is also well illustrated with malaria. Malaria is endemic throughout the tropics, with a high prevalence in Africa, the Indian subcontinent, Southeast Asia, and parts of South and Central America and Mexico. Approximately 2.4 billion people live in areas of risk, with some 350 million new infections occurring annually, resulting in approximately 2 million deaths, predominantly in young children. Untreated malaria can become a life-long affliction—general symptoms include fever, headache, and malaise.

The climate sensitivity of malaria arises owing to the nature of the interactions of parasites, vectors, and hosts, all of which impact the ultimate transmission rates to humans. The gestation time required for the parasite to become fully developed within the mosquito host (a process termed sporogony) is from eight to thirty-five days. When temperatures are in the range of 20°C to 27°C, the gestation time is reduced. Rainfall and humidity also have an influence. Both drought and heavy rains tend to reduce the population of mosquitoes that serve as vectors for malaria. In drier regions of the tropics, low rainfall and humidity restricts the survival of mosquitoes. Severe flooding can result in scouring of rivers and destruction of the breeding habitats for the mosquito vector, while intermediate rainfall enhances vector production.


^ Ketidak-seimbangan Ekologis


Cholera is a serious and potentially fatal disease that is caused by the bacterium Vibrio cholerae. While not nearly so prevalent as malaria, cases are nonetheless numerous. In 1993, there were 296,206 new cases of cholera reported in South America; 9,280 cases were reported in Mexico; 62,964 cases in Africa; and 64,599 cases in Asia. Most outbreaks in Asia, Africa, and South America have originated in coastal areas. Symptoms of cholera include explosive watery diarrhea, vomiting, and abdominal pain. The most recent pandemic of cholera involved more regions than at any previous time in the twentieth century. The disease remains endemic in India, Bangladesh, and Africa. Vibrio cholerae has also been found in the United States—in the Gulf Coast region of Texas, Louisiana, and Florida; the Chesapeake Bay area; and the California coast.

The increase in prevalence of ^ V. cholerae has been strongly linked to degraded coastal marine environments. Nutrient-enriched warmer coastal waters, resulting from a combination of climate change and the use of fertilizers, provides an ideal environment for reproduction and dissemination of V. cholerae. Recent outbreaks of cholera in Bangladesh, for example, are closely correlated with higher sea surface temperatures. V. cholerae attach to the surface of both freshwater and marine copepods (crustaceans), as well as to roots and exposed surfaces of macrophytes (aquatic plants) such as the water hyacinth, the most abundant aquatic plant in Bangladesh. Nutrient enrichment and warmer temperatures give rise to algae blooms and an abundance of macrophytes. The algae blooms provide abundant food for copepods, and the increasing copepod and macrophyte populations provide V. cholerae with habitat. Subsequent dispersal of V. cholerae into estuaries and fresh water bodies allows contact with humans who use these waters for drinking and bathing. Global distribution of marine pathogens such as V. cholerae is further facilitated by ballast water discharged from vessels. Ballast water contains a virtual cocktail of pathogens, including V. cholerae.

Two other examples of how ecological imbalances lead to human health burdens concern the increased prevalence of Lyme disease and hantavirus pulmonary disease. Lyme disease, sonamed because it was first positively identified in Lyme, Connecticut, is a crippling arthritic-type disease that is transmitted by spirochete-infected Ixodes ticks (deer ticks). Ticks acquire the infection from rodents, and spend part of their life cycle on deer. Three factors have combined to increase the risk to humans of contracting Lyme disease, particularly in North America: (1) the elimination of natural deer predators, particularly wolves; (2) reforestation of abandoned farmland has created more favorable habitat for deer; and (3) the creation of suburban estates, which the deer find ideal habitat for browsing. The net result is a rising deer population, which increases the chances of humans coming into more contact with ticks.


^ Resistensi Antibiotik dan Praktek Pertanian

Antibiotic resistance is a growing threat to public health. Antibiotic resistant strains of Streptococcus pneumoniae, a common bacterial pathogen in humans and a leading cause of many infections, including chronic bronchitis, pneumonia, and meningitis, have greatly increased in prevalence since the mid-1970s. In some regions of the world, up to 70 percent of bacterial isolates taken from patients proved resistant to penicillin and other b-lactam antibiotics. The use of large quantities of antibiotics in agriculture and aquaculture appears to have been a key factor in the development of antibiotic resistance by pathogens in farm animals that subsequently may also infect humans. One of the most serious risks to human health from such practices is vancomycin-resistant enterococci. The use of avoparcin, an animal growth promoter, appears to have compromised the utility of vancomycin, the last antibiotic effective against multi-drug-resistant bacteria. In areas where avoparcin has been used, such as on farms in Denmark and Germany, vancomycin-resistant bacteria have been detected in meat sold in supermarkets. Avoparcin was subsequently banned by the European Union. Another example is the use of ofloxacin to protect chickens from infection and thereby enhance their growth. This drug is closely related to ciprofloxacin, one of the most widely used antibiotics in the year 2000. There have been cases of resistance to ciprofloxacin directly related to its veterinary use. In the United Kingdom, ciprofloxacin resistance developed in strains of campylobacter, a common cause of diarrhea. Multi-drug-resistant strains of salmonella have been traced to European egg production.


^ Ketahanan Pangan dan Air.

Praktek pertanian juga dapat menimbulkan sejumlah ancaman bagui kesehatan masyarakat. Sebagian dari hal ini berhubungan dengan jeleknya pengolaan limbah, yang mengakibatkan sejumlah parasit dan bakteri memasuki perairan dan system suplai air minum. Hal yang lain adalah melibatkan transfer lintas spesies pathogen-patogen yang dapat menyerang binatang dan manusia.


The most recent and spectacular example is mad cow disease, known as variant Creutzfeldt-Jakob disease in humans, a neuro-degenerative condition that, in humans, is ultimately fatal. The first case of Bovine Spongiform Encephalopathy (BSE), the animal form of the disease, was identified in Southern England in November 1981. By the fall of 2000, an outbreak had also occurred in France, and isolated cases appeared in Germany, Switzerland, and Spain. More than one hundred deaths in Europe were attributed to what has come to be commonly called mad cow disease.


Pengelolaan pupuk kandang yang tidak tepat telah berdampak pada munculnya gangguan E. coli 0157:H7 di Walkerton, Ontario, Canada. Risiko kesehatan lainnya yang berhubungan dengan mal-fungsi agroecosystems adalah adanya gangguan periodic cryptosporidiosis, penyakit parasitis yang disebarkan oleh limpasan permukaan (runoff) yang terkontaminasi oleh kotoran ternak yang sakit (terinfeksi). Parasit ini menyebabkan gangguan penyakit perut dan diarrhea pada orang-orang yang immune-competent dan diarrhea-parah dan kematian pada orang-orang yang immune-compromised.


^ Restorasi Ekosistem

Patologi ekosistem dalam beberapa kasus dapat dengan mudah diatasi dengan jalan menghilangkan sumber-sumber stress. Misalnya dalam kasus-kasus degradasi ekosistem yang diakibatkan oleh penambahan bahan kimia toksik, maka penghilangan stress ini dapat memulihkan kembali kesehatan ekosistem.
1   2   3   4   5   6   7   8   9   ...   14

Place this button on your site:
essays


The database is protected by copyright ©CoolEssay 2000-2011
send message
Lectures, essays
Documents