There is a large body of literature concerning the ground measurement of vegetation and standard methodology has been described by BROWN (1954) and SHAW and BRYAN (1976). It is seldom possible to measure the botanical composition of an entire area, so the proportion of species is determined from a set of samples. The simplest values to measure are the presence or absence and frequency of species in a given area, which are closely related parameters. Presence or absence is the actual measure of the occurrence of a species in a set of sample areas; the frequency is the probability of finding a particular species in a given area, expressed as frequency percent i.e. the percent of samples in which the species occurs. Number (density) i.e. the number of individuals per unit area, is a quantitative measure of composition, and is useful in measuring changes in plant population structure, particularly of dominant species. Cover is a measure of the proportion of ground covered by the whole vegetation or individual species, as measured by the perpendicular projection of their aerial parts onto the ground, expressed as a percentage. The most usual is canopy cover which may be given on the basis of the composition of the uppermost layer or of the whole canopy. Basal cover, which is the cover attributed to the basal rooted portions of the plants may also be determined. Cover is measured by means of point samples (canopy cover), line intercept (basal cover) or estimation. Bare ground, or the absence of cover, is an important criterion of the stability of vegetation and the effects on soil erosion.
Botanical composition on a dry-weight basis may also be determined where the productivity of vegetation is being evaluated. This is an extremely tedious method because the vegetation has to be cut, separated, dried and weighed. Accordingly, indirect methods have been developed for measuring productivity; the comparative-yield method (HAYDOCK and SHAW, 1975) and, for the floristic composition, the dry-weight rank technique (t MANNETJE and HAYDOCK, 1963). Both have been combined into a sampling and computing procedure known as Botanal (TOTHILL et al., 1978).
In a study in Botswana (ANON, 1980), indicators of range deterioration were identified as an increase in bare ground, an increase in the number of shrubs and trees and detrimental changes in botanical composition of the lower layer i.e. reduction in percentage of better quality grasses or an increase in the proportion of poor quality grasses and weeds. Selected sites were sampled from the ground. Permanent transects were established with annual observations at fixed points along each transect. To make allowances for local variation, each site was divided into three sub-sites or clusters. Each cluster consisted of six transects each 25 m long and spaced. Data collection was made on vegetation cover, botanical composition of lower and shrub/tree layers and basal cover. For vegetation cover, readings were made at 25 cm intervals, 100 per transect. For botanical composition, quadrats were sampled at 5 m intervals on alternate sides of each transect; 90 samples per site. For shrubs and trees, the total number of each species over one metre tall in each of six quadrats at the end of a number of transects were counted. Samples were taken from 18 quadrats per site. Basal cover was estimated using 100 points along each transect. For greater accuracy, this could be increased to 500 points per transect. If 500 points are taken along each 25 m transect line, this would amount to 9,000 points per site. A further example of assessment of range condition in areas as large as 100,000 sq.km. is given by WILCOX (1975).
The condition of the soil resource i.e. signs of compaction and erosion can be assessed visually by aerial survey, ground observations or a combination of both. Methodology for the visual assessment of erosion status has already been described (WILCOX, 1975). Laboratory analyses can augment these observations. A wide spectrum of laboratory methods are available to assess soil properties, including gravimetric, volumetric and colormetric techniques and the use of chromatography and spectrometry. Soils can be sampled to a fixed depth, and the intensity of sampling will depend on the extent of soil variation and the desired degree of precision. Samples may be analysed separately or bulked.
It is not within the scope of this document to describe the techniques available to assess soil properties. Standard texts (BLACK et al., 1965; PAGE et al., 1982) are available where descriptions of principles, instrumentation and analytical techniques (physical, mineralogical, chemical, microbiological) are reported in detail. Useful laboratory manuals have been written by van REEUWIJK (1987), RUMP and KRIST (1988), KALRA and MAYNARD (1991), and ANDERSON and INGRAM (1993).
Many aspects of water quality can be tested in the laboratory by the methods used for soil analyses. The measurement of nitrate content using a fixed filter photometer or spectrophotometer and the measurement of electrical conductivity are described in RUMP and KRIST (1988).
Microbiological tests for estimating bacterial numbers and the presence of coliform organisms and parasites are reported by RUMP and KRIST (1988).
7.4.1. Land competition
7.4.2. Competition for crop residues
7.4.3. Competition for labour availability
7.4.4. Draught animal power
7.4.5. Asset building
7.4.6. Intensification of agriculture
Under many circumstances, it may prove difficult to ascertain the precise causes of environmental changes or degradation and indeed to quantify the effects of these changes. Although national livestock statistics may include figures for offtake and throughput of abattoirs etc., and data for export crop yields may often be available, declining trends on a national scale may not necessarily reflect environmental degradation. This is particularly true in semi-arid environments where drought results in frequent changes in total annual production. It is possible to separate the effects of drought from longer-term declines in productivity, but many years of statistics will be required to accomplish this task. There are many differing views on the seriousness of land degradation and desertification in the drylands of the world and, with few exceptions, almost no economic analyses of the impact of degradation have been successfully accomplished (BELSHAW et al., 1991).
Shifts in international market or local prices could just as easily account for a decline in production of a particular crop or livestock product as much as a decline in fertility or the availability of grazing. Therefore, it is necessary to undertake some monitoring of individual farms as well as markets and national data to assess the effect of productive activities of farmers on any changes in the environment.
Useful indicators of environmental change can, therefore, be provided if projects undertake some form of monitoring and evaluation of farmer activities. Also required will be some form of information gathering at the outset of a project to determine prevailing conditions and as a benchmark upon which to judge the effects of livestock upon the environment.
The subject of crop-livestock interactions and their economic and environmental effects suffers from a lack of information. The literature provides few indications of the relative importance of each sector to the household economy and almost no analysis of the likely environmental impact of further intensification. Therefore, it will be necessary to establish base-line data by farm and household survey before socio-economic indicators can be further developed and refined. Some of the data may already have been collected but may remain inaccessible at the national scale. It would be useful to establish some form of standardisation of data collection methods to enable comparisons to be made both within and between countries.
Data collection need not be a lengthy and drawn out process and modern methods of formal and informal surveys such as rapid rural appraisal and participatory rural appraisal allow researchers to rapidly gather information in rural areas of developing countries. Environmental change, particularly where it is rapid, can often be checked against farmer recall over periods of as much as 50 years or more.
Changes in livestock species kept by farmers can indicate a change in environmental or economic conditions. They may also however, be a response to drought.
Other indicators of environmental change may include the privatisation of crop residues in the face of declining access or availability of natural grazing; the development of a market for crop residues; the development of a market for manure; increasing conflict between farmers and herders over access to key resources (particularly dry-season grazing) and changes in the relative importance of crops or livestock to the household economy in the fact of environmental or other changes.
The most difficult task for the economist when assessing the economic impact of environmental degradation is to decide which of the environmental and resource impacts to include in any analysis and then how to quantify and monetise them (DIXON et al., 1992). It is important, therefore, to initially identify impacts and make all assumptions explicit. Changes in production can be valued using market prices although often there will be secondary effects that will also need to be quantified. For example, reduced availability of natural pasture will have a negative economic effect upon livestock herders, but if the land lost to pasture is cultivated then the value of the crop production (including crop residues) may be greater than the value of livestock production forgone (in some cases the value of the crop residues may be greater than that from degraded natural pasture). Under these circumstances the impact will be negative for the livestock producer and positive for the cultivator. Bush encroachment will have a negative effect upon cattle producers but may benefit goat producers.
Measuring the effects of land competition on the agricultural economy will require estimates to be made of the Effect on Production that it causes and the value of the change in output that results (WINPENNY, 1991). Changes in use of land may produce positive economic effects but will have serious socio-economic consequences for those people losing access to land. If cultivation is ecologically inappropriate and leads to land degradation the effect will be multiplied and will represent a long-term loss in grazing resources. If expanding areas of cultivation lead indirectly to range degradation then the economic consequences of this degradation will need to be measured and assessed.
Having determined the physical effects of environmental degradation the main data requirements will be:
· evidence of the environmental repercussions of an activity on the output of marketed goods;An alternative technique is the Preventative Expenditure and Replacement Cost approach. This involves observations of actual expenditure on safeguards to prevent further environmental damage (e.g. deferring grazing, building terraces) or expenditure and investment on land to return it to its original productive state. Information can be obtained in several ways (WINPENNY, 1991):
· data on market prices of the goods in question;
· where prices are likely to be affected, predictions of production and consumption responses;
· where output is not marketed, the price at the nearest market for that product, or for its closest substitute;
· an appreciation of the behavioral adjustments that producers and consumers are likely to make in response to environmental damage.
· direct observation of actual spending on safeguards against potential degradation or the costs of rehabilitation;If competition for land leaves livestock or crop-producing communities with little option but to encroach onto protected areas then it will be necessary to quantify the effect of this encroachment. This may require both a calculation of the potential income foregone (tourism) and also the existence value of the resource (i.e. the quality or existence of the resource will have value in terms of biodiversity even if there are no obvious user benefits).
· enquiring of people whether they are prepared to invest in land improvements or preventative methods;
· obtaining expert opinions on the cost to individuals or the state of implementing preventative actions or rehabilitation programmes.
The social consequences of degradation will need to be measured by socio-economic survey to establish the effects over time. Data collection need not be a lengthy drawn-out process as modern methods of formal and informal surveys such as rapid rural appraisal and participatory rural appraisal allow researchers to rapidly gather information in rural areas of developing countries.
As the development of markets and the privatisation of use of crop residues may indicate scarcity of fodder then measurement will require that market and socio-economic surveys be undertaken to establish the extent to which this indicator reflects actual shortages of pasture and fodder. Data will need to be integrated with time-series information on livestock populations to determine the extent to which livestock production is compromised by a shortage of feed. In other words it is important to establish whether these indicators reflect deterioration of the environment or are simply a response to growing human and livestock populations.
Under conditions of high population density and intensification of agriculture, measurement of indicators will require analysis of national statistics on wage rates, sale of animal and engine-powered machinery and adoption of yield-enhancing technologies such as fertilisers and high-yielding varieties.
As pasture becomes scarce and distances travelled by livestock to pasture increase so the effect of this change on labour availability and, in turn, its effect upon crop production will be required to be monitored. Although remote sensing may be able to indicate the seasonal movements of livestock much of this information, including details of its effect upon manure supply and household consumption of livestock products, will need to be collected directly (by survey) from the producers.
The environmental consequences of the introduction of draught animal power and their long-term economic effects have rarely been measured. Its effect upon land availability for livestock herders and increased pressure on range resources can be measured in the same manner as outlined in Section 7.4.1. Much of the information required in terms of its effect upon soil fertility and consequently upon incomes may be available, particularly if draught animals are used for the production of cash or export crops. If total areas cultivated and output are known it may be possible to establish trends over time, taking into account levels and changes in fertiliser use (if any).
The situation regarding subsistence production is more problematic as information on yields over time may not be available. It will be necessary to identify existing data and to collect further data as necessary to assess the long-term impact of the technology on household incomes and food security, including its effect upon non-users of the technology.
Measurement of indictors will require analysis of national livestock statistics to include totals and the number of livestock marketed. Measurement of the effect of increasing numbers of livestock on grazing resources are dealt with under 7.1-7.3.
Data on investment in land improvements, privatisation of land holdings and increased household income can be derived from a mixture of national statistics and socio-economic survey. Information on individual ownership of land and trends in farm size will be available from land registers, household income data and changes in returns per unit of land will require socio-economic surveys.