Konsep Ekosistem




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KONSEP DASAR AGROEKOSISTEM


Bahan kajian MK. Manajemen Agroekosistem FPUB Maret 2010

Diabstraksikan oleh

Prof Dr Ir Soemarno MS

Dosen Jur Tanah FPUB


Konsep Ekosistem


Suatu EKOSISTEM merupakab lingkungan biologis yang terdiri atas semua organisme hidup dalam suatu area tertentu, serta komponen abiotik dan komponen fisik dari lingkungan yang berinteraksi dengan organisme, seperti udara, tanah, air dan radiasi matahari. Ekosistem ini meliputi semua organisme dalam suatu area tertentu, berinteraksi dengan faktor-faktor abiotik ; merupakan suatu komunitas biologis dengan lingkungan fisiknya.


Ecosystem: Complex of living organisms, their physical environment, and all their interrelationships in a particular unit of space. An ecosystem's abiotic (nonbiological) constituents include minerals, climate, soil, water, sunlight, and all other nonliving elements; its biotic constituents consist of all its living members. Two major forces link these constituents: the flow of energy and the cycling of nutrients. The fundamental source of energy in almost all ecosystems is radiant energy from the sun; energy and organic matter are passed along an ecosystem's food chain. The study of ecosystems became increasingly sophisticated in the later 20th century; it is now instrumental in assessing and controlling the environmental effects of agricultural development and industrialization. (http://www.answers.com/topic/ecosystems-1#ixzz1f2hC3okb)


^ Definisi Ekosistem


Sistem ekologi dapat didefinisikan sebagai suatu komunitas tumbuhan dan binatang yang saling berinteraksi beserta lingkungan abiotik atau alamiahnya. Ekosistem-ekosistem dapat dikelompokkan berdasarkan vegetasi dominannya, topography, iklim atau beberapa criteria lainnya.


Boreal forests, for example, are characterized by the predominance of coniferous trees; prairies are characterized by the predominance of grasses; the Arctic tundra is determined partly by the harsh climatic zone. In most areas of the world, the human community is an important and often dominant component of the ecosystem. Ecosystems include not only natural areas (e.g., forests, lakes, marine coastal systems) but also human-constructed systems (e.g., urban ecosystems, agroecosystems, impoundments). Human populations are increasingly concentrated in urban ecosystems, and it is estimated that, by the year 2010, 50 percent of the world's population will be living in urban areas.


Suatu bentang-lahan terdiri atas mozaik ekosistem-ekosistem, termasuk kota-kota, sungai, danau, system pertanian, dsb. Batas-batas yang tepat di antara ekosistem-ekosistem tersebut seringkali sulit ditetapkan.


A functional system that includes an ecological community of organisms together with the physical environment, interacting as a unit. Ecosystems are characterized by flow of energy through food webs, production and degradation of organic matter, and transformation and cycling of nutrient elements. This production of organic molecules serves as the energy base for all biological activity within ecosystems. The consumption of plants by herbivores (organisms that consume living plants or algae) and detritivores (organisms that consume dead organic matter) serves to transfer energy stored in photosynthetically produced organic molecules to other organisms. Coupled to the production of organic matter and flow of energy is the cycling of elements.

All biological activity within ecosystems is supported by the production of organic matter by autotrophs (organisms that can produce organic molecules such as glucose from inorganic carbon dioxide; see illustration). More than 99% of autotrophic production on Earth is through photosynthesis by plants, algae, and certain types of bacteria. Collectively these organisms are termed photoautotrophs (autotrophs that use energy from light to produce organic molecules). In addition to photosynthesis, some production is conducted by chemoautotrophic bacteria (autotrophs that use energy stored in the chemical bonds of inorganic molecules such as hydrogen sulfide to produce organic molecules). The organic molecules produced by autotrophs are used to support the organism's metabolism and reproduction, and to build new tissue. This new tissue is consumed by herbivores or detritivores, which in turn are ultimately consumed by predators or other detritivores.



Model aliran energy melalui ekosistem.

http://www.answers.com/topic/ecosystems-1#ixzz1f2eXwrp3


Ekosistem darat (terrestrial ecosystems), yang meliputi 30% permukaan bumi, menyumbangkan sekitar separuh dari total produksi global bahan organic fotosintetik—sekitar 60 × 1015 gram karbon per tahun. Lautan, yang meliputi 70% permukaan bumi menghasilkan bahan organic sekitar 51 × 1015 g C setiap tahun.


^ Jaring-jaring Makanan

Organisme dapat diklasifikasikan berdasarkan banyaknya transfer energy melalui ajring-jaring makanan. Produksi bahan organic secara foto-autotrofik mencerminkan transfer energy yang pertama di dalam suatu ekosistem dan diklasifikasikan denagai PRODUKSI PRIMER. Konsumsi suatu tumbuhan oleh by a herbivora merupakan transfer energi ke dua , sehingga herbivore menempati tingkat trofik ke dua, juga dikenal sebagai PRODUKSI SEKUNDER. Organiske konsumen yang merupakan transfer ke satu, dua atau tiga dari foto-autotrof dikelompokkan sebagai konsumen primer, sekunder, dan tersier. Bergerak melalui suatu jarring-jaring makanan, energy hilang selama proses transfer sebagai panas, sebagaimana dijelaskan dengan Hukum Termodinamika ke dua. Oleh karena itu, jumlah total transfer energy jarang yang melebihi empat atau lima; dengan adanya kehilangan energy selama setiap proses transfer, maka sedikit sekali energy yang tersedia untuk mendukung organism yang berada pada tingkat tertinggi dari suatu jaring-jaring makanan.


Energy flow drives the ecosystem, determining limits of the food supply and the production of all biological resources. Light energy from the sun is captured by green plants and converted to chemical energy. Energy is stored in plants as carbohydrates and used by the plant to support all functions such as vegetative growth, fruit maturation and respiration. Other organisms use and convert this chemical energy to various forms through food chains. A food chain is a succession of organisms in a community that constitutes a feeding sequence in which food energy is transferred from one organism to the next as each consumes a lower number and in turn is preyed upon by a higher number. At the bottom of the chain is a photosynthesizing plant, usually followed by an herbivore, a successions of carnivores, and finally decomposers. At each step, some of the chemical energy is assimilated and used by the organism and the rest is released in respiration and waste products.


Jaring-jaring makanan (Food web) merupakan rantai-rantai makanan yang saling berkaitan secara “rumit” dalam suatu komunitas. Struktur trofik (^ Trophic structure) merupakan serangkaian keterkaitan dalam suatu jaring-jaring makanan yang mendeskripsikan transfer energy dari suatu tingkat nutritional ke tingkat berikutnya. Sasaran produksi tanaman adalah memaksimumkan energy ekosistem ke dalam hasil-panen; penggunaan energy tanaman oleh hama tidak diperlukan karena hal ini berarti mengambil energy dari produksi tanaman.




Dalam suatu siklus biogeokimia, unsure-unsur hara anorganik yang diperlukan untuk pertumbuhan dan perkembangan organism bersirkulasi dari komponen abiotik ke komponen biotic dan kembali lagi ke komponen abiotik dari ekosistem (Source Flint, M.L and P. Gouveia, 2001)

Sumber: http://www.knowledgebank.irri.org/ipm/index.php/ecosystem-ecology….. diunduh 29/6/2011



Diagram jaring-jaring makanan dalam alfalfa. Setiap tanda panah mencerminkan transfer makanan, atau energy dari satu organism ke organism lainnya. Jaring-jaring menjadi lebih kompleks kalau semakin banyak spesies yang dimasukkan ke dalam system. (Flint, M.L. and P. Gouveia. 2001).

Sumber: http://www.knowledgebank.irri.org/ipm/index.php/ecosystem-ecology….. diunduh 29/6/2011


^ Organisme hidup membentuk jaring-jaring makanan

The living organisms in an agro-ecosystem are the biotic component. The organisms can be analyzed as a food web that represents the transfer of material and energy from one group of organisms to another. For a food web analysis, organisms are grouped by their function in the flow of energy and nutrients rather than by their classification into genus and species. All the plants in an agro-ecosystem make up the primary producers and provide the basis of the food web. Plants capture solar energy through their leaves and in combination with water and nutrients from the soil and carbon dioxide from the air generate plant material. The next level of organisms is the herbivores that live off the nutrients and energy provided by plants or primary producers. Many different types of organisms can be herbivores - birds, insects, nematodes, fungi, bacteria and virus. In turn, the energy and nutrients in herbivores are exploited for growth and reproduction by another group of organisms called secondary consumers. Animals that live off the energy and nutrients in the substance of secondary consumers are called tertiary consumers. Many different types of organisms can also be primary, secondary and tertiary consumers.




Sumber: http://www.knowledgebank.irri.org/ipm/index.php/ecosystem-ecology….. diunduh 29/6/2011




^ Sumber: http://platforms.inibap.org/agro/concepts.html ….. diunduh 29/6/2011


The soil food web has many organisms feeding both on living and dead plant material. Thus, the many organisms derive energy to grow and reproduce and eventually nutrients tied up in plant and animal material is available again for plant growth.




^ Sumber: http://platforms.inibap.org/agro/concepts.html ….. diunduh 29/6/2011

Siklus Biogeokimia

In contrast to energy, which is lost from ecosystems as heat, chemical elements (or nutrients) that compose molecules within organisms are not altered and may repeatedly cycle between organisms and their environment. Approximately 40 elements compose the bodies of organisms, with carbon, oxygen, hydrogen, nitrogen, and phosphorus being the most abundant. If one of these elements is in short supply in the environment, the growth of organisms can be limited, even if sufficient energy is available. In particular, nitrogen and phosphorus are the elements most commonly limiting organism growth. This limitation is illustrated by the widespread use of fertilizers, which are applied to agricultural fields to alleviate nutrient limitation.


The movement of energy from one level of the food web to the next. The proportion of energy at one level of the food web that makes it to the next level is called ecological efficiency - this is usually less than 10%. In an agroecosystem, we also care about how well the energy consumed by organisms, usually either the crop plants (the producers, with energy from the sun) or livestock (herbivores, with energy from feed or pasture), is converted into body tissue - this is conversion efficiency.



Sumber: http://www.acad.carleton.edu/curricular/BIOL/classes/bio160/ClassResources/Case_Studies/Case3_Energy/Case3_Directions.htm ….. diunduh 29/6/2011


Carbon cycles between the atmosphere and terrestrial and oceanic ecosystems. This cycling results, in part, from primary production and decomposition of organic matter. Rates of primary production and decomposition, in turn, are regulated by the supply of nitrogen, phosphorus, and iron. The combustion of fossil fuels is a recent change in the global cycle that releases carbon that has long been buried within the Earth's crust to the atmosphere. Carbon dioxide in the atmosphere traps heat on the Earth's surface and is a major factor regulating the climate. This alteration of the global carbon cycle along with the resulting impact on the climate is a major issue under investigation by ecosystem ecologists.


^ Siklus Karbon


Organic chemicals are made from carbon more than any other atom, so the Carbon Cycle is a very important one. Carbon between the biological to the physical environment as it moves through the carbon cycle.

Earth's atmosphere contains 0.035% carbon dioxide, CO2, and the biological environment depends upon plants to pull carbon into sugars, proteins, and fats. Using photosynthesis, plants use sunlight to bind carbon to glucose, releasing oxygen (O2)in the process. Through other metabolic processes, plants may convert glucose to other sugars, proteins, or fats. Animals obtain their carbon by eating and digesting plants, so carbon moves through the biotic environment through the trophic system. Herbivore eat plants, but are themselves eaten by carnivores.

Carbon returns to the physical environment in a number of ways. Both plants and animals respire, so they release CO2 during respiration. Luckily for animals, plants just happen to consume more CO2 through photosynthesis than they can produce. Another route of CO2 back to the physical environment occurs through the death of plants and animals. When organisms die, decomposers consume their bodies. In the process, some of the carbon returns to the physical environment by way of fossilization. Some of it remains in the biological environment as other organisms eat the decomposers. But by far, most of the carbon returns to the physical environment through the respiration of CO2.



Sumber: http://www.starsandseas.com/SAS%20Ecology/SAS%20chemcycles/cycle_carbon.htm ..... diunduh 29/6/2011

Siklus Nitrogen

Proteins, nucleic acids, and other organic chemicals contain nitrogen, so nitrogen is a very important atom in biological organisms. Nitrogen makes up 79% of Earth's atmosphere, but most organisms can not use nitrogen gas (N2). N2 enters the trophic system through a process called nitrogen fixation. Bacteria found on the roots of some plants can fix N2 to organic molecules, making proteins. Again, animals get their nitrogen by eating plants. But after this point, the nitrogen cycle gets far more complicated than the carbon cycle. Animals releases nitrogen in their urine. Fish releases NH3, but NH3 when concentrated, is poisonous to living organisms. So organisms must dilute NH3 with a lot of water. Living in water, fish have no problem with this requirements, but terrestrial animals have problems. They convert NH3 into urine, or another chemical that is not as poisonous as NH3. The process of releases NH3 is called ammonification. Because NH3 is poisonous, most of the NH3 which is released is untouchable. But soil bacteria have the ability to assimilate NH3 into proteins. These bacteria effectively eats the NH3, and make proteins from it. This process is called assimilation.


Some soil bacteria does not convert NH3 into proteins, but they make nitrate NO3- instead. This process is called nitrification. Some plants can use NO3-, consuming nitrate and making proteins. Some soil bacteria, however, takes NO3-, and converts it into N2, returning nitrogen gas back into the atmosphere. This last process is called denitrification, because it breaks nitrate apart.




Sumber: http://www.starsandseas.com/SAS%20Ecology/SAS%20chemcycles/cycle_carbon.htm ..... diunduh 29/6/2011


Siklus Phosphorus


Phosphorus is the key to energy in living organisms, for it is phosphorus that moves energy from ATP to another molecule, driving an enzymatic reaction, or cellular transport. Phosphorus is also the glue that holds DNA together, binding deoxyribose sugars together, forming the backbone of the DNA molecule. Phosphorus does the same job in RNA.

Again, the keystone of getting phosphorus into trophic systems are plants. Plants absorb phosphorous from water and soil into their tissues, tying them to organic molecules. Once taken up by plants, phosphorus is available for animals when they consume the plants.

When plants and animals die, bacteria decomposes their bodies, releasing some of the phosphorus back into the soil. Once in the soil, phosphorous can be moved 100s to 1,000s of miles from were they were released by riding through streams and rivers. So the water cycle plays a key role of moving phosphorus from ecosystem to ecosystem.

In some cases, phosphorous will travel to a lake, and settle on the bottom. There, it may turn into sedimentary rocks, limestone, to be released millions of years later. So sedimentary rocks acts like a back, conserving much of the phosphorus for future econs.



Sumber: http://www.starsandseas.com/SAS%20Ecology/SAS%20chemcycles/cycle_carbon.htm ..... diunduh 29/6/2011

Siklus hara dalam suatu agroekosistem melibatkan tanaman, ikan dan ternak. Salah satu jalur utama aliran hara adalah jalur tanaman-ternak-tanah. KOlam ikan, jalur utamanya adalah tanaman dan ternak. Dalam beberapa kasus dalam system pertanian tradisional di Asia,, limbah manusia dan rumahtangga menjadi input penting bagi tanaman dan kolam ikan, sedangkan limbah dapur penting bagi ternak dan kolam ikan.




Sumber: Edwards (1993) (http://www.fao.org/docrep/006/y5098e/y5098e05.htm ..... diunduh 2/7/2011)


Aliran hara di antara komponebn dalam agroekosistem dan antara agroekosistem dengan system eksternalnya adalah sebagai berikut.




Sumber: Le and Rambo (1993) (http://www.fao.org/docrep/006/y5098e/y5098e05.htm ..... diunduh 2/7/2011)

Fotosintesis


Organisme dan fungsi suatu sel hidup bergantung pada persediaan energi yang tak henti-hentinya, sumber energi ini tersimpan dalam molekul-molekul organik seperti karbohidrat. Organisme heterotrofik seperti ragi dan kita sendiri, hidup dan tumbuh dengan memasukkan molekul-molekul organik ke dalam sel-selnya. Untuk tujuan praktis, satu-satunya sumber molekul bahan bakar yang menjadi tempat bergantung seluruh kehidupan ialah fotosintesis. Fotosintesis menyediakan makanan bagi hampir seluruh kehidupan di dunia baik secara langsung atau tidak langsung. Organisme memperoleh senyawa organik yang digunakan untuk dan rangka karbon dengan satu atau dua cara utama: nutrisi autotrofik atau heterotrofik. Autotro dapat diartikan bahwa dapat menyediakan makanan bagi diri sendiri hanya dalam pengertian bahwa autotrof dapat mempertahankan dirinya sendiri tanpa memakan dan menguraikan organisme lain. Autotrof membuat molekul organik mereka sendiri dari bahan mentah anorganik yang diperoleh dari lingkuannya. Oleh karena alasan inilah, para ahli biologi menyebut autotrof sebagai produsen biosfer.


Organisme heterotrof memperoleh materi organik melalui cara pemenuhan nutrisi kedua. Ketidakmampuan dalam membuat makanan mereka sendiri, menyebabkan hererotrof ini hidup tergantung pada senyawa yang dihasilkan oleh organisme lain; heteritrif merupakan komponen biosfer. Sebagian autotrof mengkonsumsi sisa-sisa organisme mati, menguraikan dan memekan sampah seperti bangkai, tinja dan daun-daun yang gugur. Heterotrof ini dikenak sebagai pengurai. Sebagian besar fungi dan banyak jenis bakteri memperoleh makana dengan cara seperti ini. Hampir seluruh heterotrof, termrasuk manusia, benar-benar tergantung pada fotoautotrof untuk mrndapatkan makanan dan juga untuk mendapatkan oksigen, yang merupakan produk samping fotosintesis.


^ Jalur Fotosintesis

Dengan keberadaan cahaya, bagian-bagian tumbuhan yang berwarna hijau menghasilkan bahan organik dan oksigen dari karbon dioksida dan air. Dengan menggunakan rumus molekul, persamaan kimia fotosintesis adalah:


6CO2 + 12 H2O + energi cahaya -----> C6H12O6 + 6O2 + 6H2O


Karbohidrat C6H12O6 ialah glukosa. Air muncul pada kedua sisi persamaan itu karena 12 molekul dikonsumsi dan 6 molekul terbentuk lagi selama fotosintesis. Persamaan itu dapat disederhanakan dengan memperlihatkan selisih konsumsi air:


6CO2 + 6H2O + energi cahaya ----> C6H12O6 + 6O2


Dalam bakteri berfotosintesis, sebagai pengganti H2O dipakai zat pereduksi yang lebih kuat seperti H2, H2S dan H2R (R adalah gugus organik). Persamaan reaksinya adalah:


2CO2 + 2H2R -----> 2C2O + O2 +2R



Bakteri menggunakan H2R dan menggunakan hidrogen untuk membuat gula. Dari reaksi kimia tersebut dapat dikatakan bahwa semua organisme fotosintetik membutuhkan sumber hidrogen, tetapi sumber itu bermacam-macam.


^ Tempat Berlangsungnya Proses Fotosintesis

Di dalam tumbuhan, proses fotosintesis pada umumnya berlangsung dalam organel khusus yang disebut plastid. Plastid mengandung senyawa, yaitu klorofil. Semua bagian yang berwarna hijau pada tumbuhan, termasuk batang hijau dan buah yang belum matang, memiliki kloroplas, tetapi daun merupakan tempat utama berlangsungnya fotosintesis pada sebagian besar tumbuhan. Terdapat ± setengah juta kloroplas tiap milimeter persegi permukaan daun. Warna daun berasal dari klorofil, pigmen warna hijau yang terdapat dalam kloroplas. Energi cahaya yang diserap klorofil inilah yang menggunakan sintesis molekul makanan dalam kloroplas.

Sebagian besar spesies tumbuhan, terpacu pertumbuhan dan perkecambahan dalam keadaan terang. Namun biji juga dapat terhambat perkecambahanyya oleh cahaya. Panjang gelombang merah jauh dari sinar matahari hampir selalu merupakan panjang gelombang yang paling menghambat. Cahaya biru juga kadang menghambat. Biji yang membutuhkan cahaya untuk berkecambah disebut fotodorman. Biji yang biasanya berkecambah dalam gelap akan terhambat oleh cahaya. Biji yang biasa berkecambah dalam gelap akan mengalami dormansi atau fase istirahat saat terkena cahaya dalam tingkat intensitas tertentu.

Cahaya tampak sebagai sumber energi yang digunakan tumbuhan untuk fotosintesis merupakan bagian spektrum energi radiasi. Reaksi cahaya dalam fotosintesis merupakan bagian akibat langsung penyerapan foton oleh molekul pigmen seperti klorofil. Tidak seluruh foton mempunyai tingkat energi yang cocok untuk menggiatkan pigmen daun. Di atas 760 nm foton tidak memiliki cukup energi dan di bawah 390 nm foton memiliki terlalu banyak energi, menyebabkan ionisasi dan kerusakan pigmen. Hanya foton dengan panjang gelombang antara 390 dan 760 nm memiliki tingkat energi yang cocok untuk fotosintesis. Karena penggiatan pigmen merupakan akibat langsung interaksi antara foton dan pigmen, pengukuran cahaya yang digunakan dalam fotosintesis seringkali berdasarkan densitas aliran foton, dan bukan berdasarkan energi. Densitas aliran foton ialah jumlah foton yang menumbuk suatu luas permukaan tertentu per satuan waktu. Karena panjang gelombang antara 400 dan 700 nm itu paling efisien digunakan dalam fotosintesis, pengukuran cahaya untuk fotosintesis biasanya didasarkan pada densitas aliran foton dalam panjang gelombang 400 dan 700 nm tersebut (Michael,1994).




Sumber: http://ecology07.blogspot.com/2011_03_01_archive.html …. Diunduh 29/6/2011

Kesehatan Ekosistem

It is important to recognize the inherent difficulties in defining "health," whether at the level of the individual, population, or ecosystem. The concept of health is somewhat of an enigma, being easier to define in its absence (sickness) than in its presence. Perhaps partially for that reason, ecologists have resisted applying the notion of "health" to ecosystems. Yet, ecosystems can become dysfunctional, particularly under chronic stress from human activity. For example, the discharge of nutrients from sewage, industrial waste, or agricultural runoff into lakes or rivers affects the normal functioning of the ecosystem, and can result in severe impairment. Excessive nutrient inputs from human activity was one of the major factors that severely compromised the health of the lower Laurentian Great Lakes (Lake Erie and Lake Ontario) and regions of the upper Great Lakes (Lake Michigan). Unfortunately, degraded ecosystems are becoming more the rule than the exception.

The study of the features of degraded systems, and comparisons with systems that have not been altered by human activity, makes it possible to identify the characteristics of healthy ecosystems. Healthy ecosystems may be characterized not only by the absence of signs of pathology, but also by signs of health, including measures of vigor (productivity), organization, and resilience.

Vigor can be assessed in terms of the metabolism (activity and productivity) of the system. Ecosystems differ greatly in their normal ranges of productivity. Estuaries are far more productive than open oceans, and marshes have higher productivity than deserts. Health is not evaluated by applying one standard to all systems. Organization can be assessed by the structure of the biotic community that forms an ecosystem and by the nature of the interactions between the species (both plants and animals). Invariably, healthy ecosystems have more diversity of biota than ecologically compromised systems. Resilience is the capacity of an ecosystem to maintain its structure and functions in the face of natural disturbances. Systems with a history of chronic stress are less likely to recover from normal perturbations such as drought than those systems that have been relatively less stressed.

Healthy ecosystems can also be characterized in economic, social, and human health terms. Healthy ecosystems support a certain level of economic activity. This is not to say that the ecosystem is necessarily self-sufficient, but rather that it supports economic productivity to enable the human community to meet reasonable needs. Inevitably, ecosystem degradation impinges on the long-term sustainability of the human economy that is associated with it, although in the short-term this may not be evident, as natural capital (e.g., soils, renewable resources) may be overexploited and temporarily enhance economic returns. Similarly, with respect to social well-being, healthy ecosystems provide a basis for and encourage community integration. Historically, for example, native Hawaiian groups managed their ecosystem through a well-developed social cohesiveness that provided a high degree of cooperation in fishing and farming activity.


^ Kesehatan Agro-ecosystem


One of the basic hypotheses in the research proposal is that the agro-ecosystem health paradigm will provide a superior conceptual framework than agricultural sustainability, which has remained 'without much empirical content because of the lack of a comprehensive definition and analytical methodology' (ILRI 1998). Of course, it is possible to distinguish between the two concepts, but for the practical purposes of this research proposal they are fundamentally similar, essentially synonymous (this comparison is developed in more detail in Smit and Smithers (1994). Once the term 'agro' is appended to 'ecosystem' we have explicitly included human components, such that 'agro-ecosystem' is fundamentally equivalent to a broad definition of 'agriculture', which includes ecological and human components.

“Sustainable agriculture” telah didefinisikan dengan berbagai cara dan sudut pandang (Smit and Brklacich 1989; Cai and Smit 1994; Smit and Smithers 1994), tetapi kebanyakan melingkupi sifat-sifat esensial yang sama. Misalnya dua definisi berikut ini:


Agri-food systems that are economically viable, meet society's need for safe and nutritious foods, while conserving natural resources and the quality of the environment for future generations (SCC 1992),


Agricultural system that can indefinitely meet demands for food and fibre at socially acceptable economic and environmental costs (Crosson 1992).


Dalam kedua hal tersebut di atas, pertanian berkelanjutan didefinisikan dengan memperhatikan:

  • Kebutuhan atau permintaan social atas pangan, termasuk gizi, dan mencerminkan kesehatan manusia

  • Kelayakan ekonomis, mengacu kepada pemeliharaan system produksi

  • Kualitas lingkungan, yang diarahkan pada kondisi sumberdaya biofisik.


Definisi “keberlanjutan” juga memperhatikan sifat-sifat ini atas waktu ('generasi mendatang” atau 'indefinite'). Definisi kesehatan agro-ecosystem melingkupi sifat-sifat esensial yang sama, yaitu:

  1. Kesejahteraan manusia

  2. Keragaan ekonomis, dan

  3. Kondisi ekologis.


Pada kenyataannya, esensi dari perspektif kesehatan agroekosistem (agro-ecosystem health, AESH) adalah bahwa ia mencerminkan eksistensi dan interrelationships di antara beberapa domain system pertanian (economi, manusia dan ekologi), dan bahwa kesehatan system secara keseluruhan merupakan fungsi dari kondisi dan interdependensi di antara komponen-komponen ini.


A simple conceptualisation of agro-ecosystem health indicates three main dimensions, which interact (hence overlapping sets), which manifest at different scales (hence the different sizes of sets), and which can be employed in numerous applications, including a) using indicators to compare systems or document changes in AESH, b) identifying and specifying relationships among dimensions to understand dynamics and determinants of AESH, and c) assessing responses in AESH to stresses, both those associated with external environments (such as climatic variations or macro-economic conditions) and those reflecting interventions or policies.


 



Kesehatan Agro-ecosystem: Suatu teladan representasi diagramatik.


Landasan konseptual dari dua paradigm ini, AESH dan agricultural sustainability (AS), pada hakekatnya sinonim. Keduanya bersifat evaluative dari keseluruhan kondisi lingkungan pedesaan, ekonomi, dan manusia. Sehingga sasarannya juga meliputi komponen ini:

  • Peningkatan ketahanan pangan

  • Pengentasan kemiskinan

  • Melestarikan kualitas lingkungan yang baik.


In other respects as well, AESH and AS are very similar. Both are applicable at different spatial and temporal scales. For both, considerable effort has been expended in developing indicators, and similar kinds of indicators (often very long lists) have been proposed. Indicators can take a wide variety of forms, including state and functional indicators, diagnostic and early warning indicators. There are also many examples of particular empirical studies employing indicators, especially of sustainable agriculture . However, neither of these frameworks can supply a single, comprehensive measurable indicator which can adequately capture the scope of these systems. Nor do either of them provide a specific set of analytical steps to document change, assess responses, or evaluate interventions in these systems. The noteworthy contribution of the agro-ecosystem health concept is a metaphor, providing a broad framework which facilitates the consideration of multiple dimensions and the interactions among them.

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