Bibliography: Land Degradation in South Africa project

of the future challenges will be to bring together conservation biology,

economics and social science in order to develop appropriate protocols for the

study of the human use of plants. Recent studies have taken steps towards this.

It is essential, however, that this blend of ecological and social science does

not result in a less rigorous approach. It should instead enhance hypothesis

formation and testing through new insights, leading to a predictive capability.

This would strengthen the means to influence policy on conservation and

management of regional plant resources.

Ref ID : 1689

660. Curry-Lindahl, K. The conflict between development and nature conservation

with special reference to desertification. In: Ecosystem theory and application,

edited by Polunin, N.John Wiley & Sons Ltd. 1986,

Reprint : In File,

Keywords : CONSERVATION; RESTORATION; POPULATION; LAND USE; LEGISLATION;

POLITICAL ASPECTS; SOCIOECONOMIC ASPECTS; METHODOLOGIES; PRODUCTION POTENTIAL;

VELD MANAGEMENT; WATER CONSERVATION; DESERTIFICATION CONTROL; PLANT-ANIMAL

INTERACTIONS; ENVIRONMENTAL POLICY

Notes : Conflicts between development and nature conservation, with special

regard to desertification, are primarily dependent on two totally different

approaches. Development schemes, chiefly because of social and political

considerations, almost always base their planning on short-term views by

emphasizing quick economic returns and immediate results from the investiments

made, whereas conservation, being based on ecological considerations,

necessarily must rely on long-term aspects involving at least an ecosystem

dimension of sustained productivity and yield as well as some restoration of

what Man has already destroyed. The short-term approach of development projects

is connected with the human population increase, 'land hunger', economic

pressure, traditional and often adverse land-use methods, lack of political and

social courage to apply existing legislation and/or take energetic measures to

stop the ongoing devastation of renewable resources - for example of water,

soil, vegetation, and wild animals. The long-term, conservation approach pays

due consideration to the useful interactions of these resources and to the

interest also of future generations of human beings. In most deserts and semi-

deserts, native plants and animals provide lessons to Man on how to survive in

dry environmental conditions. A basic prerequisite for increased productivity

would be a major reduction, and locally even elimination, of domestic livestock

herds and their replacement by native wild animals. The latter would allow the

vegetation to recover, whereupon the optimal population-size of the wild

herbivores would be determined by the plants. Thus the great symbiosis of

plants and animals would be functioning again. In other areas, a combination of

wild and domestic animals may constitute rational utilization of semi-arid

rangelands; but on really arid lands the superiority of the wild herbivores as

being more productive than domestic ones while at the same time avoiding

environmental damage, is widely evident. The need for new approaches to land-

use practices must be combined with education schemes for the rural nomadic

populations concerned, if further drastic desertification is to be avoided.

Ref ID : 289

661. D'Huyvetter, J.H.H. and Laker, M.C. Determination of threshold slope

percentages for the identification and delineation of Arable land in Ciskei.

1985.

Reprint : Not in File,

Keywords : SOIL EROSION; CULTIVATION; SUSTAINABLE DEVELOPMENT; FARMING SYSTEMS;

LAND USE; DESERTIFICATION CONTROL; COMMUNAL AREA; EROSION CONTROL; CISKEI;

EASTERN CAPE

Notes : Final report to the CSIR.

Ref ID : 1691

662. Dahlberg, A. Contesting views and changing paradigms: the land degradation

debate in southern Africa.Anonymous Uppsala:Nordiska Afrikainstitutet. 6, 1994.

Reprint : In File,

Keywords : LAND DEGRADATION; SOUTHERN AFRICA; VEGETATION CHANGE; LAND TENURE;

DESERTIFICATION ASSESSMENT; METHODOLOGIES

Notes : Innumerable books, articles and reports have been written on the subject

of degradation and environmental change in southern Africa. To write a

literature review of a subject as vast as this is to invite criticism concerning

the approach taken, the topics and views presented and the references selected.

When, as here, the aim is to review contesting views and changing paradigms, the

subjective choice of contents, as well as of what is left out, sets a personal

mark on the text that is not always encountered in a review. The topics

discussed in this review are numerous, but many relevant issues have been left

out or mentioned only briefly. For example, the effect of tenure on

environmental change and degradation, and the use of environmental impact

assessments, are two important aspects of the debate that this review only

alludes to. These and other omissions are due to the necessity of limiting the

scope and size of the text, and are not the result of any value judgements.

Similarly, although the reference list is long, many valuable studies have been

left out. What is hoped to have been achieved is a summary of approaches

adopted, of the type of conclusions presented, and an overview of the

contradictions and conflicts in the debate.

Ref ID : 1694

663. Dahlberg, A. Interpretations of Environmental Change and Diversity: A study

from North East District, Botswana.Environment and Development Studies Unit,

Department of Physical Geography, Stockholm University, Sweden. , 1996. Studies

of environmental change in semi-arid Africa often present contraditory results

as regards the magnitude, severity and causes of observed changes. Some central

questions are how findings may be generalised and extrapolated, how perceptions

of the environment are recognised and analysed, and how various value-judgement

terms are derfined and used. Emerging theories about ecosystem dynamics, and the

growing awareness of the value of an interdisciplinary approach, form the

background of the present study of an agro-patoral area in the North East

District, Botswana. Since the beginning of the centrury, this area has been

described as subjected to severe land degradation due to high population density

and overstocking. Processes of environmental change during the last 60 to 100

years are related to land-use practices and livelihood strategies, as well as to

outside interventions. Specific environmental outcomes are linked to different

'types' of change, e.g. short and long-term effects of isolated events, of

cyclic variations, and of trends. Further, the spatial heterogeneity of the

landscape is taken into account, and also differences in how the environment is

perceived. Aerial photographs, soil and vegetation sampling, and in-depth

interviews, were some of the tools used. On several issues the present results

contradict previous descriptions of the area. Instead of increasing land

degradation, a situation of fluctuating environmental conditions was identified.

Many environmental changes were found to be caused by isolated physical or

social events, and the duration of the new conditions could vary considerably.

Other changes occurred in cycles, often with superimposed random events. As for

long-term 'causative' trends, the few that were identified showed a small and

uncertain impact on the environment, especially in comparison with the influence

of short-term fluctuations. Several environmental variables commonly used as

indicators of degradation (especially of overgrazing) were identified and found

to vary in time and space. However, present conditions were hardly ever the

result of effectively irreversible processes. Instead they constitute stages in

environmental cycles caused by human land use in conjunction with natural

variability. The heterogeneity of the landscape, the erratic and fluctuating

rainfall, and the differences in land use, are the main causes of the

environmental variations in time and space. The studied landscape is strongly

marked by a long period of human land use. Against this background, few signs

of detrimental environmental changes were identified. Further, the

understandingsing of processes of change, expressed by local land users,

corresponds quite closely to recent re-thinking of ecosystem dynamics of semi-

arid areas.

Reprint : In File,

Keywords : BOTSWANA; LAND DEGRADATION; POPULATION; LAND USE; RAINFALL;

VEGETATION CHANGE; ENVIRONMENTAL HISTORY; METHODOLOGIES; VEGETATION DYNAMICS;

STOCKING RATE; SATELLITE IMAGERY; VELD CONDITION; SOCIOECONOMIC ASPECTS; GRAZING

EFFECTS; DESERTIFICATION ASSESSMENT

Ref ID : 2125

664. Dallas, H.F. An Evaluation of SASS (South African Scoring System) as a Tool

for the Rapid Bioassessment of Water Quality.University of Cape Town. , 1995.

Reprint : Not in File,

Keywords : WATER QUALITY

Notes : Unpublished M.Sc. Thesis.

Ref ID : 2126

665. Dallas, H.F. An assessment of the current status of aquatic

macroinvertebrate communities of the Diep River system, south-western Cape,

using SASS4.Anonymous Cape Town:Southern Waters Ecological Research and

Consulting, Freshwater Research Unit. , 1997.

Reprint : Not in File,

Ref ID : 2127

666. Dallas, H.F. and Day, J.A. The effect of water quality variables on

riverine ecosystems: a review.Anonymous Water Research Commission. TT61/93,

1993.

Reprint : Not in File,

Keywords : WATER QUALITY

Ref ID : 2128

667. Dallas, H.F., Day, J.A., and Reynolds, E.G. The effects of water quality

variables on riverine biotas.Anonymous Water Research Commission. 351/1/94,

1994.

Reprint : Not in File,

Keywords : WATER QUALITY

Ref ID : 1208

668. Danckwerts, J.E. A technique to assess the grazing capacity of sweetveld

with particular reference to the False Thornveld areas of the Ciskei.University

of Natal, Pietermaritzburg. , 1981. Abstract in file.Master of Science.

Reprint : In File,

Keywords : CARRYING CAPACITY; CISKEI; COMMUNAL AREA; EASTERN CAPE; FARMING

SYSTEMS; GRAZING EFFECTS; RURAL DEVELOPMENT; STOCKING RATE; VELD CONDITION; VELD

MANAGEMENT; CLIMATE; MODELS; RAINFALL

Notes : Overstocking has been identified as the overriding factor responsible

for the extensive degradation of veld in the Ciskei. This situation results

from the socio-economic climate prevailing in the territory, which is that there

has been little incentive for farmers to achieve normally acceptable levels of

animal production. A survey of stocking rates currently applied in the Ciskei

shows that they are well above those recommended for the various regions in the

territory. The recommended stocking rates are themselves a gross overestimation

of the carrying capacity of the veld, being based on what the carrying capacity

would be, were the veld in good condition. Trends in livestock numbers in the

Ciskei suggest that there is no significant progress being made to reduce the

stocking rates currently applied. The sweetveld areas in the Ciskei are the

most severely overstocked in the territory. The current investigation is aimed

at developing a technique to record grazing capacity in sweetveld, and to

formulate a preliminary model to predict grazing capacity in the False Thornveld

of the Eastern Province, one of the most severely overstocked veld types in the

Ciskei. The investigation is aimed specifically at the grass, as opposed to the

woody component, of vegetation. A review of techniques used to assess optimum

stocking rates, or grazing capacities of swards, reveals that they fall into two

categories: those using clipping trials, and those using grazing experiments.

Both approaches have serious limitations for assessing the grazing capacity of

sweetveld. The chief limitations are that these techniques are generally

orientated not toward improvement or maintenance of veld condition, but rather

to maximum production of animal products per unit input; and that experimental

areas required are generally large. A procedure is proposed for recording

grazing capacity on sweetveld. The technique is specific for rotational grazing

systems, and experimental treatments simulate individual camps in such systems,

thus greatly reducing the size of grazing experiments. Grazing capacity is

recorded from the number of grazing days per ha up to the point where swards

just begin to be overgrazed, summed over all periods of occupation during the

grazing season. Three means of optimising grazing days per ha during periods of

occupation are suggested: the number of grazing days per ha until an arbitrarily

set "lenient" utilisation intensity is reached; the number of grazing days per

ha up to the point where the rate of depletion of herbage deviates from

linearity (the point where insufficient quantity of herbage on offer restricts

intake), and the grazing pattern sequence approach were grazing days per ha are

optimised at the point where the distribution of herbage (as recorded by the

frequency distribution of disc meter readings) reaches a maximum deviation from

normality through skewness. Optimisation of grazing days per ha by any of these

approaches is largely dependent on the use of the disc pasture meter. The

instrument has thus been assessed on natural veld in the False Thornveld of the

Eastern Prpovince. The use of the standard disc pasture meter is found to be a

reliable technique for estimating the yield of the densely tufted grass swards

found in the veld type. It compares favourably with traditional methods of

yield estimation. Is attractiveness lies in the rapidity with which yield

estimates can be made, and the non-destructive nature of sampling. This latter

property enables the instrument to be used to identify the point where the rate

of disappearance of herbage deviates from linearity during periods of

occupation, and to study animal selection patterns. The most important factors

affecting grazing capacity in the False Thornveld are considered to be: veld

condition; the quantity and distribution of seasonal and annual rainfall; the

level of sophistication of grazing management; and the density of woody species.

Other parameters such as the edaphic environment also influence grazing

capacity, but are likely to be less important in the veld type as a whole. The

proposed technique was used to record grazing capacity over a range of veld

condition types under two separate simulated rotational grazing systems. In the

first case, treatments simulated camps in a system where only one grazing per

year takes place. In the second case, treatment simulated camps in a practical

and reasonably sophisticated management system for the area; a twelve camp

system with a third of the area rested annually and an average period of

occupation of two weeks. Treatments were situated on the University of Fort

Hare Research Foarm. Veld condition on all treatments was recorded by method of

Foran et al. (1978), adapted for use in the False Thornveld. The point where

herbage disappearance deviated from linearity during a period of occupaton was

considered the most appropriate technique for optimisation of grazing days per

ha. The arbitrarily set lenient utilisation intensity approach overestimated

grazing capacity on veld in good condition and underestimated grazing capacity

on veld in poor condition. The grazing pattern sequence approach, while

promising, was not successful on swards grazed more than once per year. A

relation between grazing capacity and veld condition was not derived from swards

grazed more than once per year. These treatments were largely designed to test

the proposed technique for recording grazing capacity. A highly significant

linear relationship was obtained between grazing capacity and veld condition on

treatments simulating camps in the reasonably practical management system. The

effect of grazing management on grazing capacity was extrapolated from the

results of a clipping trial, conducted on the University of Fort Hare Research

Farm. All combinations of three frequences and three intensities of defoliation

were applied at three veld condition sites during a single growing season.

Treatment effects were recorded during the season of application, and their

carry over effects recorded during the subsequent season. Veld condition had

greatest influence on herbage yield. Frequency and intensity of defoliation

affected yield to a lesser degree, but this was manifested both during the

season of application of treatments and in the subsequent season, their effect

being greatest on veld in good condition. There was no significant interaction

between frequency and intensity of defoliation, making it impossible to compare

various grazing management philosophies. Frequency of defoliation alone did

have a significant effect on yield, and this result was used to derive a

relation between grazing capacity and the number of camps allocated per group of

animals. This relation suggested that camp number has little short term effect

on grazing capacity. The effect that total rainfall over the previous twelve

consecutive months has on grazing capacity was determined from annual herbage

yield and corresponding rainfall data, recorded over a range of twelve month

periods and a range of sites in the veld type. The variation in grazing

capacity could be only partially explained by variation in the previous twelve

months rainfall. However, most of the error could be explained by variations in

veld condition between the sites where yield was recorded. The effect the

density of woody species has on grazing capacity was extrapolated form the

results of Aucamp (1980c). The density of woody species does not affect grazing

capacity in the veld type up to a tree density of 1 000 trees per ha, after

which grazing drops linearly with increasing tree densities. The relations

between grazing capacity and the four parameters under consideration were used

to formulate a preliminary model to predict grazing capacity in the False

Thornveld of the Eastern Province. The form is set out in the summary. The

models express grazing capacity in terms of grazing per ha. On treatments used

to determine the relation between grazing capacity and veld condition,

cumulative gains per ha were recorded progressively during each period of

occupation. These were used to formulate factor/product relations between

grazing days per ha and live mass gain per ha, in order to relate maximum

profitability to intensity of herbage utilisation in beef production systems in

the False Thornveld of the Eastern Propvince. The most profitable utilisation

intensity for veld in good condition and under a reasonably sophisticated

management sysetm was found to be biologically acceptable in the veld type.

This result is used to justify a proposal to impose a cash economy on pastoral

agriculture in less developed Black States in South Africa in order to

facilitate veld rehabilitation in these areas.

Ref ID : 1720

669. Danckwerts, J.E. The grazing capacity of sweetveld: 2. A model to estimate

grazing capacity in the False Thornveld of the Eastern Cape. Proceedings of the

Grassland Society of southern Africa 17:94-98, 1982.

Reprint : In File,

Keywords : MODELS; EASTERN CAPE; RAINFALL; GRAZING EFFECTS; CARRYING CAPACITY;

STOCKING RATE; VELD MANAGEMENT; VELD CONDITION; LIVESTOCK PRODUCTION

Abstract : The relations between grazing capacity and three independent

variables were investigated in the False Thornveld of the Eastern Cape. The

variables were veld condition, rainfall and the density of woody species. These

relations were used to develop a preliminary model to assess grazing capacity in

the veld type. Despite its preliminary nature, grazing capacities calculated

using the model compare favourably with those estimated by experienced pasture

scientists, and with the stocking rate actually applied on veld that is

considered to be excellently managed.

Ref ID : 1721

670. Danckwerts, J.E. The grazing capacity of sweetveld: 1. A technique to

record grazing capacity. Proceedings of the Grassland Society of southern Africa

17:90-93, 1982.

Reprint : In File,

Keywords : STOCKING RATE; EASTERN CAPE; CARRYING CAPACITY; VELD MANAGEMENT; VELD

CONDITION; LIVESTOCK PRODUCTION; GRAZING EFFECTS; FARMING SYSTEMS

Abstract : A technique is proposed for measuring the grazing capacity of sweet

grassveld. The suggested prodecure is to record the parameter on plots

simulating individual camps in rotational grazing systems. This allows

considerably smaller experimental areas to be used than in conventional stocking

rate trials. Grazing capacity is assumed to be the number of grazing days per

hectare that can be obtained on a sward, provided animals perform at their

maximum capabilities for that sward. This is determined from the point where

the rate of herbage disappearance deviates from linearity during periods of

occupation. The technique was tested, and found to work well, under two

simulated grazing management systems in the False Thornveld of the Eastern Cape.

Ref ID : 1329

671. Danckwerts, J.E. Die dier/plantwissel-werking. Weiding 'n strategie vir die

toekoms.Anonymous Anonymous Pretoria:Departement van Landbou en

Watervoorsiening. :1-16, 1989. 0 621 12057 X.`.

Reprint : In File,

Ref ID : 1286

672. Danckwerts, J.E. The animal/plant interaction. Grazing management: a

strategy for the future.Anonymous Anonymous Pretoria:Deparment of Agriculture

and Water Supply. :1-15, 1989. 0 621 12056 1.

Reprint : In File,

Notes : Grazing animals affect pastures by defoliation, by treading and by

excretion. Each of these factors affects forage production, forage quality and

botanical composition, and each factor in turn is affected by these pasture

characteristics. There is, therefore, no simple cause and effect relationship.

In addition, many of the effects and pasture characteristics are influenced