Land-use change and climate

Human activities in Australia and world-wide cause, or contribute to, desertification, deforestation, salinization and soil erosion, and also to reforestation, irrigation and landscape ‘management’. Human-induced land-use changes impact on the Earth's climate both locally and on a larger scale, right up to disturbance of the general circulation and hence the global climate. People have become a major environmental agent acting on the future climate through land-use change, particularly deforestation (and reforestation), desertification (which often includes overgrazing and excessive exploitation of vegetation), agricultural expansion, and soil erosion and degradation. The largest impact of land-use change on the future climate seems likely to be as a result of enhanced greenhouse gas emissions. At the same time, rapidly increasing populations, especially in the tropics, demand additional food, water for drinking and cleaning, and materials for the construction of shelters—all of which depend upon sustaining a reasonable climate. Climate and human land-use requirements are linked, but the closeness of that link varies from intimate dependency to callous disdain. In this paper, the impacts of human-induced land-use changes on future climate are explored in the context of the projections of global climate models.     

Land use,deforestation and reforestation in the Zambian Copperbelt

Temporal and spatial changes in land use, vegetation cover, deforestation and reforestation in the Zambian Copperbelt were studied using a combination of aerial photograph analysis, literature review and inquiries among relevant government institutions. The study showed that between 1937 and 1984 loss of natural woodlands in the Copperbelt of Zambia (total area of Copperbelt: 9,615 km²) amounted to 41 per cent woodland area (8,419 km²). The major causes of this deforestation are woodfuel collection (for firewood and charcoal), cultivation and replacement of natural woodland with forest plantations. These accounted for 38 per cent, 37 per cent and 15 per cent of the total deforestation, respectively. Before 1962 the copper mining industry used large quantities of firewood to generate electricity and this resulted in the loss of 150,413 ha of woodland between 1937 and 1961. When the mining industry switched to hydroelectricity, urban households became the major users of woodfuel. The urban population in the Copperbelt increased from 0.412 million in 1960 to 1.400 million in 1984 and its consumption of woodfuel led to the deforestation of at least 89,436 ha between 1962 and 1984. Deforested areas are left to regenerate naturally. However, due to poor management about 34 per cent of the area deforested before 1962 has failed to regenerate. Although 50,200 ha have been reforested with exotic trees, only 5,020 ha of this is on land previously deforested. Thus only about 10 per cent of reforestation efforts have contributed to the rehabilitation of damaged land. Ninety per cent of the reforestation has actually replaced standing indigenous woodland. Uncontrolled bushfires have destroyed forest plantations and have also caused the failure of woodland regeneration in deforested areas. These observations indicate that if forest resources in the Copperbelt of Zambia are to be properly managed it will be necessary:

• 1 to effectively regulate land use changes and;
• 2 to control bushfires.

     

Land use change and net C flux in Indian forests

This paper reports on the net carbon flux caused by deforestation and afforestation in India over the period from 1982 to 2002, separately for two time periods, 1982–1992 (PI) and 1992–2002 (PII), using the IPCC 2006 guidelines for greenhouse gas inventories. The approach accounts for forest and soil C pool changes for (a) forest areas remaining as forests, (b) afforested areas and (c) deforested areas. The data set used were remote sensing based forest cover for three time periods (1982, 1992, 2002), biomass increments, biomass expansion factors and wood density. In addition a number of required coefficients and parameters from published literature were adopted. In the 1982–2002 period, the forest cover changed from 64.20 Mha in 1982 to 63.96 and 67.83 Mha in 1992 and 2002 respectively. During the PI and PII periods, plantations were also established of 0.2 and 0.5 Mha yr⁻¹, while the annual deforestation rate was about 0.22 and 0.07 Mha in these periods, respectively.     

Rapid deforestation and fragmentation of Chilean Temperate Forests

The temperate forests of Chile are classified a biological “hotspot” as a result of their high species diversity and high endemism. However, they are being rapidly destroyed, with significant negative impacts on biodiversity. Three land-cover maps were derived from satellite imagery acquired over 25 years (1975, 1990 and 2000), and were used to assess the patterns of deforestation and forest fragmentation in the coastal range of south-central Chile. Between 1975 and 2000, there was a reduction in natural forest area of 67% in the study area, which is equivalent to an annual forest loss rate of 4.5% per year using a compound-interest-rate formula. Forest fragmentation was associated with a decrease in forest patch size, which was associated with a rapid increase in the density of small patches (<100 ha), and a decrease in area of interior forest and in connectivity among patches. Since the 1970s, native forest loss was largely caused by an expansion of commercial plantations, which was associated with substantial changes in the spatial configuration of the native forests. By 2000, most native forest fragments were surrounded by highly connected exotic-species plantations. The assessment of forest loss and fragmentation provides a basis for future research on the impacts of forest fragmentation on the different component of biodiversity. Conservation strategies and land use planning of the study area should consider the spatial configuration pattern of native forest fragments and how this pattern changes over time and space at landscape level.     

Soil quality degradation processes along a deforestation chronosequence in the Ziwuling area, China

Accelerated erosion caused by deforestation and soil degradation has become the primary factor limiting sustainable utilization of soil resources on the Loess Plateau of Northwestern China. We studied the physical, chemical, and microbiological processes of soil degradation along a chronosequence of deforestation in the Ziwuling area of northwestern Shaanxi province. The results indicated that soil wet aggregate stability, mean aggregate diameter decreased with years following deforestation. Accelerated erosion resulted in soil nutrient loss, and a decrease in soil enzyme activities including notable losses of total soil N, organic C, alkaline phosphatase activity, and invertase activity. During the early time period, the rates of total soil N, organic C, alkaline phosphatase activity, and invertase activity decreasing were rapid and gradually decreased with deforestation years. Increased use of nitrogen fertilizers made determination of soil quality based on measured NO₃–N and NH₄–N inconclusive. The differences in measured parameters between the topsoil and subsoil horizons decreased with time since deforestation, and we concluded that soil erosion was the primary process responsible for the degradation of measured soil physical, chemical, and microbiological properties.     

Deforestation and land use effects on micromorphological and fertility changes in acidic rainforest soils in Venezuelan Andes

With the aim of determining the impact on soil caused by deforestation and replacement by pasture in the rainforests of the Venezuelan Andes, three representative plots were selected: one under natural forest (F), another deforested (D), and the third one under pasture (P). The chemical analyses of the soils were complemented with a micromorphological study. The analysis of thin sections revealed major differences in the microstructure and porosity, as well as in the characteristics of the fine fraction and organic constituents, together with other pedological features, corroborating the different dynamics and types of soil in the natural or altered forest landscape. The change in soil use leads to the reorganization of the solid fraction, evidenced in the intensity of the processes of transference and accumulation of materials in the different soil horizons. The results confirm that the change in land use is determinant in the current fertility and evolution of the soils. The main consequences of the land-use change are: a change in the soil organic-matter cycle with a greater degree of maturation in the disturbed soils (C/N in Ah horizon: 28.5 (F); 19.8 (D); 18.4 (P)), in which moder humus from undisturbed forest soils transforms into an acidic mull in the anthropogenic disturbed ones; illuviation of organic matter and minerals appears to have occurred after deforestation (colour (dry–wet) in Ah–Bt1–Bt2 horizons: 3/2–2/2, 4/4–3/4, 4.5/4–3.5/4 (F); 5/4–4.5/4, 5/6–4/6, 5/6–4.5/6 (D); 4.5/4–4/3.5, 5/6–4/4, 5/6–4/4 (P)); the amount of kaolinite and the degree of browning increased gradually with deforestation; other changes observed (bioturbation, microstructure, porosity and distribution of organic constituents) may also be related to the different activity of the soil fauna in disturbed (oribatids) and undisturbed soils (worms). Thus the porosity changes in the following form: the percentage of packing voids in the surface samples decreases from a 80% in the forest soil to a 70% and 65% in deforested and pasture soils, respectively. Moreover in depth a dominance of channels in forest-soil porosity changes into an abundance of planar voids in the other two types of soils studied.     

Declining abundance of American ginseng (Panax quinquefolius L.) documented by herbarium specimens

American ginseng (Panax quinquefolius L.) is a native North American forest herb whose roots have been collected for their reputed medicinal properties and exported to international markets for nearly 300 years. Numerous anecdotal reports suggest declining abundance throughout its range, and the species is currently listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. This study examines the putative decline of American ginseng over the last 150 years in 19 US states by using data from herbarium specimens. For successive time intervals, we calculate the numbers of American ginseng specimens in addition to the numbers of specimens of related taxa that are not commercially harvested. The proportions of American ginseng specimens from adjacent time intervals are then examined for significant changes. An additional analysis evaluates the potential for species overrepresentation in the database due to species collection bias. Despite evidence of preferential collection of American ginseng, the proportion of American ginseng specimens declined significantly through time for six northern states. This result is consistent with a long and intense history of harvest, extensive deforestation in northern regions of the United States, and slow regeneration of American ginseng.     

Three decades of deforestation in southwest Sumatra: Effects of coffee prices, law enforcement and rural poverty

In situ conservation of tropical forests often requires restricting human use and occupancy within protected areas by enforcing regulations. However, law enforcement interventions that seek to prevent deforestation rarely have been evaluated. Conservationists increasingly recognize the need to measure the effectiveness of their interventions, using an indicator of biodiversity change, such as rate of deforestation, and a counterfactual approach that addresses a fundamental question: what would have happened had there been no intervention? This study examines how law enforcement can mitigate habitat loss from small-holder coffee growing by comparing 34 years of empirical data on deforestation rates and coffee prices across a zone of high law enforcement and a zone of low law enforcement using satellite imagery, ecological data, interviews, and GIS modeling.In the early 1980s strong law enforcement efforts were found to reduce deforestation inside Bukit Barisan Selatan National Park (BBSNP), southwest Sumatra. However, law enforcement efforts were weak in remote areas of BBSNP, where high coffee prices spurred rapid deforestation. Furthermore, law enforcement efforts were reversed by the 1997-1998 Asian economic crisis, the fall of the national president, and by new regulations surrounding regional autonomy. These findings indicate that law enforcement is critical but insufficient alone. They also highlight that rising costs of agricultural commodities can be detrimental to tropical forests and their associated biodiversity. In the long run one must act to decrease the incentives for coffee cultivation. A multi-faceted strategy that includes law enforcement and incentives to reduce poverty around PAs is proposed.     

Tree diversity and carbon stocks of some major forest types of Garhwal Himalaya,India

Four forest stands each of twenty major forest types in sub-tropical to temperate zones (350 m asl–3100 m asl) of Garhwal Himalaya were studied. The aim of the study was to assess the stem density, tree diversity, biomass and carbon stocks in these forests and make recommendations for forest management based on priorities for biodiversity protection and carbon sequestration. Stem density ranged between 295 and 850 N ha⁻¹, while total biomass ranged from 129 to 533 Mg ha⁻¹. Total carbon storage ranged between 59 and 245 Mg ha⁻¹. The range of Shannon–Wiener diversity index was between 0.28 and 1.75. Most of the conifer-dominated forest types had higher carbon storage than broadleaf-dominated forest types. Protecting conifer-dominated stands, especially those dominated by Abies pindrow and Cedrus deodara, would have the largest impact, per unit area, on reducing carbon emissions from deforestation.     

Native vegetation and its ecosystem current situation in Brazil

GeographyandclimateBrazilIiesinsouthernhemisphere.withanareaof8.511.965km',9OpercentofthecountryiswithinthetropicalzoneTherearefiveclimaticregionsinBrazilfequatorial.tropicaI.semi-arid,highlandtropical,andSubtroplcaIThereisneitherbIisteringheatnorse-verecoldTheannuaIaveragetemperatureintheAmazonregionisintherangeof22-26"C.almostnoseasonalvariation,temperaturesofabove32"CarerarelyhappenedthereNortheastisthehottestpartwithtemperaturesofmorethan38'Cindryseasons.AlongtheAtlanticcoast,annuaI…