Project Amazonia: Solutions - Sustainable Land Management - Agricultural Plan
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Problem addressed:
The posseiros (landless peasants) are using unsustainable agricultural practices in the Amazon. This is a major cause of deforestation.
Plan:
To solve this problem, we plan to implement agroforestry practices in the Amazon amongst the posseiros. We want to experiment with original models of integrated agroforestry farms that use the subsistence techniques of the indigenous people.
Background:
· The difficulties of the posseiros:
The difficulties faced by the posseiros in finding and farming land are explained in the background section of land demarcation solution.
Historically, development policies have tended to overlook the large population of small farmers living on poor land. They have focused primarily on best lands and on the refinement of input-intensive production systems, such as those found in the southern regions. The difficulties faced by the posseiros have not been addressed, even though solutions to their problems would have considerable environmental and socioeconomic benefits and would offer an alternative solution to the problem of deforestation1.
· Common agricultural practices
Shifting cultivation is the most common practice throughout the forest. As traditionally practiced, it is well suited to the forest; it recycles nutrients, conserves soil and water, allows for diversity of crops and allows long fallow periods in the cultivation cycle. But this traditional cultivation becomes less sustainable as population rises and as migrants unfamiliar with the rainforest attempt to farm newly cleared land. Shifting cultivation is now associated with disastrous deforestation effects2.
Monocultural systems are not very successful in the Amazon. Their equilibrium is too fragile to resist the various threats of the complex environment (vulnerability to pests and weeds). They are also harmful to the environment, causing a reduction in biodiversity, the depletion of nutrients, and runoff during rainfalls3.
· Constraints on agricultural productivity:
Biological productivity requires solar energy, water and nutrients. These are all available in the rainforest, so there is the potential for efficient agricultural production in the Amazon. However, the existing agricultural systems do not reflect this productive potential. This can be explained by a variety of socioeconomic and environmental constraints:
- High temperature and humidity restrict the types of crops and animals that can be raised and favor the spread of pests and diseases. The climatic conditions also result in high post harvest losses to pests and spoilage and pose problems for storage, transportation and processing4.
- As explained in characterization section in greater detail, the Amazonian soils have low nutrient reserve, high aluminum toxicity, high acidity, deficiency in phosphorus and susceptibility to erosion. None of these factors are conducive to agricultural activity.
- Pests, pathogens and weeds can greatly decrease productivity. In 1990, the US Agency for International Development that pests and pathogens caused pre-harvest losses of 36% and post-harvest losses of 14.
- The loss of domestic and wild biodiversity also have negative effects on productivity. The repeated use of a limited number of conventional cereal staple crops reduces the diversity of local varieties of crops. Many of these local crops are highly adapted to local climatic conditions, so they would be very profitable if they could be preserved and used sustainably.4
· Concepts of agroforestry
Agroforestry is a system of land-use which utilizes both agriculture and multipurpose tree planting.3 These two components are combined spatially and temporally. If it is run well, this system offers agronomic, environmental, and socioeconomic benefits for small-scale farmers with poor resources.
The use of trees:
Trees, preferably native ones, are an important component of a healthy farm. Trees can provide food (such as fruits, nuts, and honey), lumber, firewood, shade, and shelter. Simultaneously, they can help the environment by protecting the soil from erosion and leaching. This maximizes soil cover and minimizes the loss of nutrients5. The use of native trees will ensure that the trees are tolerant of the acidic soil and compatible with the region. Also, the addition of leguminous crops and some other tree species can be beneficial for nitrogen fixation.
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o Management of organic matter: Organic matter management practices can improve soil and water conservation during the cropping period. This improves crop yields and hastens the recovery of the system during the fallow season. A continuous ground cover must be maintained during the cropping period.3 Management methods include multiple cropping and the spatial mixture of perennials and non-perennials. Perennials have deeper roots and higher canopies than annuals. This allows for better management of above- and belowground resources. The deep-rooted perennials recycle the nutrients from the subsoil, which can than be used by the annuals. Atmospheric nitrogen can be fixed by the leguminous perennials and used by the annuals, while the difference in the depth of the roots minimizes competition for water. Perennials produce allelopathetic compounds (metabolic substances released by plants that bio-chemically inhibit other plants or microorganisms), which can suppress weeds. The differences in canopy height reduces the competition for light4. o Alley cropping and buffer zones: Annual food crops can be grown in the alleys between rows of fast-growing, nitrogen-fixing trees and nutrient-cycling trees. This helps to sustain crop productivity, through soil protection, nutrient cycling, and reduction of weed pressure. The alleys must be pruned often to provide manure and mulch for the crops and to minimize shading and root competition. Suitable native species for acidic soils are the following: - Inga edulis: Grows to a height of 30 m. Its branches form a broad, flat, moderately dense canopy. It grows well on poor soils and floodplains. It yields popular fruits which can be sold on the market. It can also be used as fodder for pigs. Its litter is high in nitrogen, lignins and polyphenols, making it an excellent leguminous species for weed control6. - Gliricidia sepium: 2-15 m tall. It has deep roots and can grow on disturbed sites and acidic soil, with pH 4.5. It has numerous uses: the flowers can be fried and eaten, goats gain in weight and productivity when they are fed its protein-rich leaves, the flowers attract honeybees (we could add honey production to the farm), the wood is used for firewood and charcoal production, the termite-resistant timber is good for house construction, furniture or for mother posts, the leaves when properly processed can be used as a pesticide, extracts have anti-fungal activity, is currently used as a remedy for boils, bruises, burns, colds, debility, fever, gangrene, headache, itch, ulcers, urticaria, and wounds6. - Flemingia macrophylla: 1-4 m tall. It also has deep roots and can survive on poor soils and highly acidic soils (pH 4.6). It requires good weed control, but once it is established, it needs little attention. It can yield about 12t/ha of leaf dry matter per year, which can be used as green manure6. - Calliandra calothyrsus: small shrub (about 5-6 m). It has both superficial and deep growing roots and is a good colonizer of disturbed sites. It grows on a variety of soils, tolerating acidic and poor soils. It grows quickly, is easy to regenerate, and needs weeding during the first year only. It should pruned regularly to avoid shade on the neighboring crops, but dense spacing is possible. Its leaves and pods are rich in protein and can be used for fodder for any ruminant. It can be used for apiculture; it is also a good firewood species (15-40 t/ha) and a good charcoal producer. Its pulp can be used for papermaking. Its large yield of green manure makes it well-suited for recovering land exhausted by agriculture. It dominates undesired weeds. It engages in symbiosis with rhizobium bacteria and root fungus for the fixing of nitrogen6. Buffer zones have to be kept between fields, for many reasons. They allow for a rapid regeneration of the forest. They also maintain the local ecosystem and habitats, and they attract wildlife. They can be used for extractive activities (mushrooms, berries, medicinal plants, nuts, resins, oils…) as well as for fishing and hunting. Additional high-value species can be planted in them, including valuable medicinal plants. It is especially important to keep a buffer zone along the margin of a river (called a riparian buffer zone), because the vegetation in the buffer zone enhances and protects aquatic resources from adverse impacts of agricultural practices. This stabilizes eroding banks, filters sediments, nutrients, and animal waste from agricultural runoff, and provides shade and food for aquatic organisms6. This buffer zone is also necessary during the period when the river invades the floodplain.
o Adaptation to the cycles of the environment: the need for an integrated approach The work done by other groups on the characterization of the ecological cycles of the forest will help us adapt the agricultural practices to the ecosystem. The application of ecological concepts and principles to the study, design, and management of sustainable agricultural systems is called agroecology and is a fundamental field of study for the preservation of the rainforest. Its goal is “to understand how physical conditions, soils, water, nutrients, pests, biodiversity, crops, livestock and people act as interrelated components of agroecosystems.”4 There is still much research to be done in this field, so we aim to conduct research studies and then incorporate our results into our plan. An integrated system would allow complementation between different elements and the ways in which they use resources. It is important to understand that in such a fragile environment, development plans have to adhere to the ecosystems.
o Rotation crops: variant to the shifting cultivation system Fallows need to be managed in the agriculture system to allow the soil to regenerate between two cropping periods. Within the system, fields should be rotated between cultivation and rejuvenating crops. The latter are usually nutrient accumulating species (they accumulate the nutrients in their biomass). These permit the harvest of useful, high-value materials (nuts, resins, medicinal plants, etc.), and they create favorable microhabitats for wildlife and for the germination of secondary fallow species4. A well-managed tree fallow needs a soil that has not been completely depleted, good regeneration of the forest on and/or around the fallow area and a long enough period of fallow to permit complete regeneration of the fallow5.
o Preservation of the nutrient cycle: There are scarce but essential nutrients which must be recycled efficiently within the ecosystem. Root growth is concentrated in the topsoil. Litter decomposes quickly and the plant nutrients are mineralized and adsorbed by the forest roots. Rain, dust and biological fixation of nitrogen add nutrients to the cycle. Steep areas with young soils suffer more important nutrient losses. Agricultural systems should not be established in such sites. In grain crops, about 40% of the carbon and 60% of the nitrogen and of the phosphorus are removed during the harvest while potassium, calcium and magnesium remain in the crop residues. In an agroforestry system, nutrient loss during harvesting would be balanced by nutrient input from manure, litter from the trees, and biological fixation of nitrogen. As crop residues are returned to the soil, they are broken down by the flora and the fauna. They are then available for the crop uptake. Then, loss will happen only if crop residues are removed from the system, if the soil is lost through erosion (this risk is tremendously reduced if the soil carries trees), or if soluble nutrients remain in the soil, with no crops grown, during heavy rains. Nitrogen deficiency is easily overcome by the use of nitrogen-fixing plants. Lack of phosphorus is more problematic. Phosphorus pumping from the deeper soil layers is limited by subsoils with toxic levels of aluminum and low phosphorus reserves. The problem can be somewhat alleviated by the deposit of phosphate rock in the fields. Adding phosphorus to the soil in association with mycorrhizal fungi is very efficient because this fungi help phosphorus uptake by the plant4. Recycling is the key idea to keep the nutrients in the system. Litter from the perennials should be harvested for burning, as well as any detritus from crops and animals. After the litter is burned, its ashes can be returned to the soil. They introduce Ca2+ and Mg2+, which raises the pH values from highly acidic to nearly neutral, and they reduce the amount of toxic Al3+.4
o Weed and pest control Weeds and pests are major threats to the farm. There are such diverse species of weeds that we cannot really propose to use chemical herbicides. Ideally, weeding should be done every 6 weeks. Some indigenous people say that, after 6 weeks, the weeds enter a growth spurt so rapid that it is difficult control them. Also, after this period, the weeds start going to seed. This weeding should be done by hand; this is far more effective than weeding with a machete. Working by hand allows one to pull out the weeds by the roots without damaging the cultigens. Since the soil is usually sandy, the weeds come out rather easily. The machete should only be used in the case of vines or plants with nettles, thorns or sharp edges. The amount of time and effort involved in weeding depends heavily on the kind of soil and the number of years for which the field has been in cultivation, but the average efficiency is between 1 and 2 m2 /minute. The farmer should be careful to weed when the weeds are young, because it will ease his work. Farmers should avoid settling on a land with a lot of clay, because this makes weeding very painful. Also, if the fields are not kept in fallow sufficiently long and are cultivated too intensively, grasses can take over, which are even harder to get rid of than weeds7. Each harvesting should be accompanied by a thorough weeding before the replanting. Then, between harvests, while the crop is maturing, weeding can be done less frequently. These weeds can be dried and burned so that their nutrients can be returned to the soil. Pest management is more complicated, especially when the objective is to minimize the use of pesticides. The use of pesticides is not very well suited to the chemistry of the Amazon. It can negatively affect the metabolism of plants, making them more susceptible to pests and diseases. In addition, since there are on average 200 different pests and diseases in the tropics which can affect one plant, it is very difficult to target pests with pesticide.8 In general, it is better to keep the ecosystem as close as possible to its original state, and the use of fertilizers and pesticides should be avoided. As an alternative to pesticides, knowledge of natural biological processes in the crop and animal production can lead to effective pest management. Integrated pest management (IPM) is now an important field of study. It relies on mortality factors, such as pest predators, weather and crop management8. Since our current knowledge of pest control is sparse, this will be a major subject of study in our experimental farm. The model which we are developing is already conducive to pest control, because the use of intercropping techniques is a major controlling agent, as is the cultivation of native species which are already resistant to local pests. Also, since fertilizers are known to cause an increase in pest densities, a farm free of fertilizers should be less prone to pests
o Fishing and hunting: The major source of protein for the indigenous people comes from hunting and fishing. The forested river margin should be used for fishing, but this use should be restricted to about 40% of the river margin, so that there is a distinction between human use areas and animal refuge areas. This helps to ensure that fishing activity is not harming wildlife. It is very important to preserve the forest on the river marginsm because the fish derive their food from substances that fall into the river from the banks and from the annual floods9. At the time of the floods, "the rivers swell and overflow the banks, merging the aquatic life and terrestrial realms. Fish gorge themselves-spreading through the flooded forest and feeding on the abundance of forest foods only then available" (Chernela 1987). Fishing can be done in the riparian buffer zone during the floodplain period and when the river is lower. It is an activity easily taken on by children with hooks and lines or with nets. Fishing is a very secure source of food. One is almost always sure to catch at least small fish. The main species caught are prochilodus nigricans, pimelodus maculates, serrasalmus, pimelodina flavipinnis. These species will have to be carefully surveyed during the testing period to check the sustainability of fishing. A study made amongst the Machiguenga (indigenous population) revealed that about .48 kg of edible food is produced per hour when fishing. It might be possible to optimize this rate with some more efficient techniques. It seems that two hours are needed to gather enough for a meal for a family of six people7. Hunting is also an important component of subsistence life in the forest. The orchards or the buffer zones are good reserves for game and animals such as wild pigs, paca coati, deers, macaus, agoutis, peccaries, pacas, and armadillos. They can be hunted with fire arms, machetes or bows and arrows. This activity should not disrupt the ecosystem or health of these species, if it is maintained as a subsistence activity. In fact, markets are already well supplied in Brazil with meat from raised animals, so the risk of transforming this hunting activity into a profit activity is low. These species will still have to be well monitored.
· extraction of NTPs (non-timber products): The high degree of biological diversity within the forest is reflected in germplasm resources and in the wide array of established and potential products which they contain. The rainforest is a source of various foods (including animal protein), spices, medicines, resins, oils, gums, pest control agents, fuels, fibers, and forages. Many of these products are only known by the indigenous people and could both be used for subsistence purposes at the local level by the posseiros and for broader economic use within a sustainable development framework. These products are so useful for subsistence purposes that the Kayapo Indians create "resource islands" of trees, shrubs, herbs and root crops by collecting seedlings in the forest and transplanting them into clearings10. - Medicinal value of plants: Many plants and animals contain genetic material and chemical compounds which are useful in the development new pharmaceuticals and other products. In the research done by scientists, the plants have mainly been investigated for only one of their biological functions (often cancer-related). It is very difficult to estimate the number of species that may be useful medicinally, but the indigenous people have considerable knowledge of these plants, and this knowledge should be catalogued so that it is not lost forever. Some examples of therapeutic agents discovered through ethnomedical knowledge are: mandrake, henbane (which yields scopolamine), coca leaf, opium (morphine, codeine), curare (tubocurarine), calabar bean (physostigmine), digitalis (digitalis glycosides), and cinchona (quinine). Unfortunately, the percentage of drugs derived from plants has steadily decreased in Northern countries, and the richness of the biome is still untapped. In developing countries, however, these drugs are still the main source of medication. - Vegetable oils and fats: For species with fruits containing glyceride oils, plantation is usually unnecessary, since there is sufficient natural abundance. Some species have been selected by indigenous people and adapted to plantation, such as: buriti palm (Mauritia flexuosa) tucuma (Astrocaryum) -> red pulp oils (market to be developed) babacu -> lauric type oil, already commercialized pupunha or peach palm-> good native specie for propagation in areas which have been cleared (possible use in starting fallow). The oils and fats are used for: ß-carotene in food (buriti, tucuma and piquia oils), base components for cosmetics (from ucuuba fat, butter-like pequia pulp oil and bacaba oil), analgesic and anti-inflammatory creams (andiroba oil), and salad oils (pataua pulp-oil). - Animal feeds: Animal feeds can be made out of residues of vegetable oil manufacture. The cellulosic fibers can be converted to digestible food for the ruminants by steam explosion. Oil-cakes (from Brazil nuts and kernels) are good food for non-ruminants. A high-protein native plant called caraparu can be found in very large amounts near mouth of Jari river. It provides an inexhaustible supply of raw material for animal feed. - Essential oils: rosewood (can also be used for soil improvement and in alley cropping), pataqueira, cumaru-tonka bean These species are good items for local community production because they are easy to produce and sold at a good price through distributors in retail market. The support from a central clinical laboratory is necessary for quality control (such a scheme has been very successful in Bolivia with Canadian IDRC participation). Cooperation with the Brazilian government and foreign pharmaceutical agencies can be useful for the processing of these products. - Insecticides and pest control agents Example: Derris roots produce rotenone concentrate, which is a natural insecticide. It can be used instead of petrochemical derived pesticides and labeled as organic. Other species: quassia, amara (sucking insect control) , carapa (mosquito and chigoe flea repellent). Such markets have an estimated potential yield of hundreds of millions of dollars. - Balsams and resins Balsams and resins can be extracted from the bark of the Amazon trees. They serve to protect the tree from microbial agents and fungi, so they can be used as an antibacterial. Here are two examples: copaiba oil treats inflammations and acts as skin antiseptic and the resin from Vismia species can be dissolved in alcohol and act as an anti-fungal. The current market organization for such products involves many intermediates. This raises the price, making it unprofitable5.
All these native plants are a great potential resource for the sustainable development of Amazonia. Some would be most efficiently developed by large companies, while others can be harvested on a smaller scale and sold on local markets. We will use some of these marketable species in the buffer zones of our model farm. Others can be marketed through the Institute of Agroforestry or the Agency the creation of which we are proposing in our plan. · interesting indigenous practices: Traditional systems and indigenous knowledge, refined over generations of trial and error, provide great insight into how to manage the forest, soils, waters, crops, animals and pests of the Amazon. It can also aid in the discovery of unexpected resources native to the forests. A lot of research has been carried out by anthropologists to assess the different practices of the more than 200 groups of indigenous people. We think this knowledge should be used by the posseiros to develop their land sustainably in addition to agroforestry practices. By reading some of the results of this research we can propose examples of practices which could be tried on the farm as experiments. We also think it would be very positive environmentally and socially to organize collaborative relationships between researchers, indigenous people and the posseiros. · potential markets Opportunities for less well-known crops may exist if the market is developed. Promising products include the peach palm, achiote (colorant), guarana (for its use in flavoring soft drinks), Brazil nuts, fruits used in juice concentrates and the various resins and oils listed above. The educational program run by the Agency of Agroforestry should include some marketing advice (what product to sell, where, etcetera). Of course, the medicinal plants offer the possibility of a lucrative market, but this has to be promoted and controlled by governmental agencies in coordination with foreign pharmaceutical companies. This is one of the objectives of ACDIK (see demarcation of indigenous land solution).
Procedure: Because agroforestry requires a relatively long time to implement, proper planning is necessary. We will first develop a model:
Location: State of Parà/longitude: 1°07'30''S /latitude: 51°07'30"W The agricultural potential of the soil is ranked as D (regular): deficiency in nutrients and high concentration in aluminum. This is the most common trend in the rainforest, especially along the Amazonas where most of the settlers are. The soil is mainly composed of fine sand with a little clay, which is appropriate for the farming practices discussed. The pH is around 4.5, the same acidity observed throughout the Amazon11. This location is near navigable waterways and roads, therefore the local markets are accessible without further infrastructure construction. It is not currently been used by other settlers, so we will not run into social objections. We confirmed this by looking at the image from Embrapa's GIS imagery.
The species: Staple crops:
Cassava is a very good staple crop: its starch-filled roots consist of 30% starch (the maximum concentration of starch among food crops), but very little protein. These roots are prepared very much like potato and can be prepared in various manners. Proteins can be found in the young tender leaves (8 to 10%) and are used in the same way as spinach. Cassava needs at least 8 months of warm weather before harvesting and it can be grown excessive rain, though it is most productive in full sun. It exist in soil whose pH between 4.0 and 8.0. There is no mature stage for cassava. Plants are ready for harvest as soon as there are storage roots large enough to meet the tastes of the consumer. Under the most favorable conditions, yields of fresh roots can reach 90 t/ha while average world yields from most subsistence agricultural systems are 9.8 t/ha. In the tropics, plants can remain un-harvested for more than one growing season, allowing the storage roots to enlarge further. The harvest is done by hand with the help of levers and ropes. If the farmer has enough money, a mechanical harvester has been developed for this crop. During the harvesting process, the cuttings for the next crop are selected. These must be kept in a protected location to prevent desiccation. Cassava presents a toxic risk: it contains high levels of cyanogenic glucosides which can be very harmful, but are rendered innocuous if well-cooked14.
Experiments to be run on the farm: Some practices which have been very successful in indigenous agriculture could be tested on this more sedentary agricultural system. These are some tentative examples which can be expanded upon as we discover more about the local ecosystem and the alternative practices of the indigenous people. - The Kayapo Indians gather a variety of forest plants and replant them near their settlements to create artificial concentrations of flora, also called "forest fields". They use about 50 species, including several types of wild manioc, wild yams, and cupa. This strategy of plant semi-domestication has almost never been used by non-indigenous farmers and could be used in the buffer zones designed on the farm. - The Kayapo also employ soil regeneration techniques. They pile sticks, limbs and leaves into mounds, let them rot, and then beat them into a mulch. This mulch is transported to sites and left to drain. The collected water is then mixed with soil from termite mounds and ant nests. These new patches of mulch are about 0.5 meters deep and 1-2 meters wide. Over time, they grow into large mounds (around one hectare in ten years) which can be used for gardening. This technique could be used for reforestation, or to garden more demanding crops in flood plain areas9. - Researchers have shown that the indigenous peoples manage their land successfully because they work in harmony with the natural ecosystem. The cultigens used by the cultivators are placed in niches that would normally be occupied by plants with similar growth characteristics and resource requirements. For example, bananas should replace Heliconia (low shady areas), uvilla should replace Cecropia and guava, shimbillo.
Survey of the farm: Through experimentation, we shall try to increase the profits of the farm. The overall objective is to create a self-sustained farm that would also interact with domestic markets. The farms will be monitored regularly to evaluate how well the crops are being grown. They will be altered according to recommendations ascertained from the monitoring data, and they will continue to run new experimental practices throughout the duration of the experiment.
Tools and requirements: To slowly build links between the peasants and the indigenous, and to teach the posseiros sustainable practices, we propose the creation of an Institute of Agroforestry in the state of Parà, consisting of botanists, zoologists, ecologists, geologists, economists, and anthropologists. Their mission would be to compile data from their respective fields to aid the posseiros. Workshops grouping indigenous people, posseiros, and members of the Institute would be organized for each major settlement of peasants. This Institute would also be responsible for checking the quality of the land allocated to the peasants by the state, using the techniques explained in the indexation of the health of the forest. The Institute should send social workers to educate the peasants about their land rights and duties and about how the land distribution system works (see land demarcation solution). The Institute could also run various agricultural experiments on the farms. The Institue would also create a germplasm bank that would be easily accessible to the peasants.
Testing: Over a five year period, we can measure the time that it takes to set these new practices in motion. We should be able to estimate the farm’s profit and determine whether there are any missing components the ecosystem of the farm. We will have to monitor the quality of the soil, in order to help the landowners manage fallow periods and crop rotation. In general, the key factor which will assess the success of the farm is the overall stability of the system. This should be looked at in terms of production rate, economic profit, flowing cycles and environmental impact. We do not know how the climatic variations might affect the overall stability of the farm or which components are the most vulnerable. This will be defined in the course of the experiment. The growth of the markets onto which new products are launched (especially NTPs with high-value products) will have to be controlled, and marketing strategies will have to be adapted to the economical landscape. A thorough monitoring of fish and game species being used by the family should also take place.
Expected results: We expect to come up with a sustainable farm which could be utilized for at least 15 to 20 years. This farm should yield long and short-term benefits (fast-growing crops, slow-growing timber, medicinal plants, game, and regenerated land, for example). The farm should be more productive and produce more of a staple food supply than more classical systems. We expect the surrounding forest to stay in its original state and not suffer any pressure from this agricultural system. Species and germplasm diversity within the agrosystem should be preserved.
1: "Sustainable Agriculture and the Environment in the Humid Tropics", edited by the National Research Council (1993) 2: "Land, people and planning in contemporary Amazonia", Center of Latin American Studies, Cambridge 3: "Planning for Agroforestry", edited by WW. Budd, I. Duchhart, L.H Hardesty, F. Steiner 4: "Sustainable Agriculture and the Environment in the Humid Tropics", edited by the National Research Council (1993) 5: "Chemistry of the Amazon: biodiversity, natural products and environmental issues" edited by P.R Seidl, O.R Gottlieb, M.A Coelho Kaplan. 6: www.worldagroforestrycentre.org 7: "Adaptive Responses of Native Amazonians", edited by R.B Hames, W.T Vickers 8: "Race to save the tropics", edited by Robert Goodland. 9: "Indigenous peoples and tropical forests" by J.W Clay. 10: "Indigenous peoples and tropical forests" by J.W Clay. "Sustainable Agriculture and the Environment in the Humid Tropics", edited by the National Research Council (1993) 11: Negreiros, Gustavo, Perfis de solos da Amazônia (RADAM, EMBRAPA, SUDAM e FAO), 1997 12: "Peasant farm size and family size: a causality analysis from the Peruvian Amazon", O.T Cornes, F Grimarie, V. Diaz, Dpt. of geography, McGill University. 13: From Ecological Agriculture Projects (http://eap.mcgill.ca/Indices/ind_cp.htm) 14: http://www.hort.purdue.edu/newcrop/Crops/CropFactSheets/cassava.html#Crops%20Status 15: http://www.extento.hawaii.edu/kbase/crop/crops/i_guava.htm#PROPAGATION 16: http://www.extento.hawaii.edu/kbase/crop/crops/i_banana.htm |
