Agroekosistem

Reintegration

The reintegration of agricultural systems into more natural systems will result in decreased yield and produce a more complex system, but there will be considerable gains in biodiversity and ecosystem services.

Biodiversitas

The FAO memperkirakan bahwa lebih dari 40% dari lahan di muka bumi saat ini digunakan untuk pertanian. Begitu banyaknya lahan yang telah dikonversi menjadi lahan pertanian, maka hilangnya habitat telah menjadi pendorong hilangnya keanekaragaman hayati (FAO). Hilangnya keanekaragaman hayati ini seringkali terjadi dalam dua tahap, dengan system pertanian campuran yang dilakukan pada lahan-lahan sempit dan kemudian dengan meluasnya penggunaan pertanian mekanik dan monokultur. Penurunan keanekaragaman hayati lahan pertanian dapat ditelusuri dari perubahan praktek pertanian dan peningkatan intensitas pertanian.

Peningkatan keaneka-ragaman

Heterogeneity (the diversity or complexity of the landscape) has been shown to be associated with species diversity. For example, the abundance of butterflies has been found to increase with heterogeneity. One important part of maintaining heterogeneity in the spaces between different fields is made up of habitat that is not cropped, such as grass margins and strips, scrub along field boundaries, woodland, ponds, and fallow land. These seemingly unimportant pieces of land are crucial for the biodiversity of a farm. The presence of field margins benefits many different taxa: the plants attract herbivorous insects, will which attract certain species of birds and those birds will attract their natural predators. Also, the cover provided by the no cropped habitat allows the species that need a large range to move across the landscape.

Monokultur

In the absence of cover, species face a landscape in which their habitat is greatly fragmented. The isolation of a species to a small habitat that it can’t safely wander from can create a genetic bottleneck, decreasing the resilience of the particular population, and be another factor leading to the decline of the total population of the species. Monoculture, the practice of producing a single crop over a wide area, causes fragmentation. In conventional farming, monoculture, such as with rotations of corn and soybean crops planted in alternating growing seasons, is used so that very high yields can be produced. After the mechanization of farming, monoculture became a standard practice in corn-beans rotation, and had broad implications for the long-term sustainability and biodiversity of farms. Whereas organic fertilizers, had kept the soil’s nutrients fixed to the ecosystem, the introduction of monoculture removed the nutrients and farmers compensated for that loss by using inorganic fertilizers. It is estimated that humans have doubled the rate of nitrogen input into the nitrogen cycle, mostly since 1975. As a result, the biological processes that controlled the way crops used the nutrients changed and the leached nitrogen from farmland soils has become a source of pollution.

Pertanian Organik

Organic farming is defined in different legal terms by different nations, but its main distinction from conventional farming is that it prohibits the use of synthetic chemicals in crop and livestock production. Often, it also includes diverse crop rotations and provides non-cropped habitat for insects that provide ecosystem services, such as pest control and pollination. However, it is merely encouraged that organic farmers follow those kinds of wildlife friendly practices, and as a result there is a great difference between the ecosystem services that similarly sized but distinctly managed organic farms provide. A recent review of the 76 studies concerning the relationship between biodiversity and organic farming listed three practices associated with organic farming that accounted for the higher biodiversity counts found in organic farms as compared to conventional farms.

1. 
   Prohibition/reduced use of chemical pesticides and inorganic fertilizers is likely to have a positive impact through the removal of both direct and indirect negative effects on arable plants, invertebrates and vertebrates.
   
2. 
   Sympathetic management of non-crop habitats and field margins can enhance diversity and abundance of arable plants, invertebrates, birds and mammals.
   
3. 
   Preservation of mixed farming is likely to positively impact farmland biodiversity through the provision of greater habitat heterogeneity at a variety of temporal and spacial scales within the landscape.
   

Degradasi Ekosistem

Degradasi ekosistem: Degradasi atau destruksi lingkungan alam sekala luas. Kalau suatu ekosistem mengalami gangguan akibat dari peristiwa alam atau kegiatan manusia maka sangat sulit untuk menghitung dampak yang dialami oleh seluruh alam. Kalau dua atau lebih ekosistem mengalami degradasi maka peluang terjadinya destruktif sinergistik akan berlipat-ganda. Ecosistem-ekosistem di banyak daerah akan terancam, dengan segala kekayaan biologisnya dan potensi manfaat materialnya. (Source: WPR)

Degradation of Coastal Environments and Potential Effects on Coastal aquaculture

(Guidelines for the promotion of environmental management of coastal aquaculture development (based on a review of selected experiences and concepts). FAO Fisheries Technical Paper. No. 328. Rome, FAO. 1992. 122 p. )

The coastal zone as an economic entity provides sites for a wide range of activities, such as agriculture (e.g., rice, coco palm, bananas), forestry (e.g., mangrove, nypa palm), fisheries and aquaculture, human settlements, manufacturing and extractive industries (e.g., sand mining, oil, minerals), waste disposal, ports and marine transportation, land transportation infrastructure, water control and supply projects, shore protection works, tourism and recreation. The multiple resource uses or activities in coastal areas may produce a variety of changes in environmental or socio-economic conditions, which in turn may result in an impact of social concern.

It is important to recognize that in many coastal areas, pollution and habitat modification stemming from human activities other than aquaculture are increasingly affecting resource use productivity of aquaculture as well as limiting success and development possibilities of the aquaculture industry.

Sumber: http://www.fao.org/docrep/T0697E/t0697e04.htm ..... diunduh 20 Desember 2011