Progressive Deforestation Research Articles

(Best Student Poster Award) Energy Harvesting from Carbon Dioxide Capture through an Ionic Liquid Based Supercapacitor

Nowadays, Earth is undergoing effects of climate change due to the exponential increase of greenhouse gasses's emissions. The main component of greenhouse emissions is carbon dioxide (CO2), which is estimated responsible for about 60% of global warming generated by human activities, and its concentration is increased by 40% with respect to the concentration at the beginnings of industrial era. This increase is due to several factors such as the combustion of coal, oil and gas and the progressive deforestation: this last phenomenon generates a sort of bottleneck in the so called biogeochemical "carbon cycle". Deforestation causes the lack of one of the natural regulating sources of carbon dioxide concentration.Scientific community set an increase of 2°C (with respect to the pre-industrial global temperature) as the threshold beyond which there is a much higher risk that dangerous and possibly catastrophic changes in the global environment will occur. At the moment the increase of the temperature has reached about +0,85°C thanks to greenhouse gasses. All technologies developed in CO2 capturing have to be intended in the reduction of global warming.The goal of the presented work is to develop a device able to cut down greenhouse emissions by reusing human produced carbon dioxide. This can be done exploiting the free energy released each time two solutions with different compositions are mixed. Even if this phenomenon holds true both for liquids and gases, in last decades it was deeply investigated for what concerns liquid sources (CapMix), while few technologies are available to harvest free energy coming from gas sources. The adopted structure is an electrical double layer super-capacitor based on ionic liquid electrolyte. Special attention should be paid to the choice of the electrolyte which should work both as an electrolyte and CO2 absorbing medium in a CapMix cell. Among the tested ionic liquids, the choice fell on an Imidazole based ionic liquid, which showed excellent absorption rates of gas, being able to capture 15.67% of CO2 over the total mass.This work is a proof of concept of a novel not yet studied mechanism, which is able to work without any imposed external bias. When a CO2 gas stream is flushed through the supercapacitor, the gas strongly affects the electrode/IL interface and the IL physico-chemical properties, producing a change in the potential difference between the electrodes. In this way it is possible to convert the mixing energy into electrical energy. Figure 1

Human-induced fires and land-use change in Lubusz Land (western Poland) derived from Lake Lubińskie sedimentary record

Sediments of Lake Lubińskie were investigated to track human-induced vegetation and fire activity changes in Lubusz Land (western Poland). Geochemical data, as well as pollen, macrocharcoal, and statistical analyses (CONISS, CharAnalysis, PCA, BINCOR) allowed us to recognize the major phases of the human impact. At the beginning of the investigation period, 3000 years ago, the area had already experienced disturbances from humans caused by the Lusatian and Przeworsk cultures, followed by western Slavs, and modern society. Land cover changes were mostly related to deforestation and gaining arable lands. The forest communities shrank substantially also due to timber demand from the growing society. However, the pollen record shows that within the last ~50 years the area experienced forest regeneration. Wildfires played an important role in shaping the landscape in the area of Lake Lubińskie. Overall, 23 fires were identified within the profile showing relatively high fire frequencies (up to 4.8 fires per 500 years) between 600 −38/+36 BCE and 1 ± 206 CE as well as between 1065 ± 98 CE and 1380 ± 92 CE. The highest fire frequency was observed between the 1000s and mid-1400s, showing decreased fire return interval (FRI) and increased charcoal flux as well as progressive deforestation. These changes were related to the establishment of villages (e.g., Lubin village) and the presence of the Joannites. Fire was most commonly used as a land management tool to gain patches of land for agrarian purposes. PCA and BINOCR analyses suggest that most of the fires were set by humans, but natural causes of ignition cannot be excluded. The land-use changes affected the vegetation in the region, causing increased erosion and shifts in the geochemistry of the lake reflected in better bottom waters ventilation and progressive eutrophication.

Diversity of Culicoides (Diptera: Ceratopogonidae) in Rural Settlements and Degraded Seasonal Deciduous Forests.

Biting midges are widespread in Brazilian natural ecosystems. However, deforestation and other activities that impact the environment are reducing natural habitats where biting midges proliferate. The objective of this study was to verify whether there is variation in the composition, richness, abundance, and seasonality of biting midges between wild and rural environments, in a forest area with intense deforestation. Biting midges were captured using 6 traps installed at an average height of 1.5 m in the peridomicile, intradomicile, and deciduous seasonal forests, once a month from May 2012 to April 2013. In total, 2,182 specimens of 13 species of the genus Culicoides were captured. Species richness was similar in the intradomicile (13 species), forest (12), and peridomicile (11), but species diversity was greater in the peridomicile (H' = 0.803) compared with the intradomicile (H' = 0.717) and forest (H' = 0.687). The order of species dominance varied between the forest (Culicoides paucienfuscatus Barbosa > Culicoides leopodoi Ortiz > Culicoides foxi Ortiz > Culicoides ignacioi Forattini) and peridomicile + intradomicile habitats (C. paucienfuscatus > C. foxi > C. filariferus Hoffman > C. ignacioi). The activity of these dipterans was strongly influenced by meteorological variables, as biting midges are predominant in the rainy season (80.7% of specimens), when higher rainfall, relative humidity, and lower temperatures prevail. The abundance of biting midges was higher in the peridomicile + intradomicile (83.7% of specimens) compared with the degraded forest (16.3%), a result that reflects the loss of forest habitat due to intense and progressive deforestation.

Degradation of a transgressive coastal Dunefield by pines plantation and strategies for recuperation (Lagoa Do Peixe National Park, Southern Brazil)

The transgressive dunefield of the Lagoa de Peixe Natural Park was modified drastically due to intensive pine plantation and the leeward development of the associated degraded areas. The present study analyzed the disturbances in the dunefield of the Lagoa do Peixe Natural Park due to pine tree plantation and the impact of the subsequent deforestation program conducted in the region. Aerial photographs, satellite images, and DGPS topographic data collected over a 70-year-long period were retrieved, analyzed, and compared, which allowed the observation of the geomorphological evolution of the dunefield. In addition, a profile of GPR on the inlet (during a period with the channel closed) was analyzed. In 1948, the surface of the sand barrier was occupied by high transverse dunes and low barchan dunes. Pine tree plantation on the inner side fixed the transgressive dunes and, consequently, avoided the filling of the shallow lagoon, although degraded areas were generated on the lee side of the pines. Simultaneous pine plantations in the backshore avoided the aeolian sediment input to the dunefield, generating a large interdune area along with the development of a few parabolic dunes, which resulted in cannibalization of the transgressive dunes. In 2001, pine trees occupied 15.03% of the total area analyzed in the present study, while the degraded area accounted for 10.81% of the total area. Progressive deforestation was performed (ring bound technique for tree gradual death), maintaining three lines of pines in contact with the dunes, to promote autochthonous vegetation growth, thereby preventing the filling of the adjacent lagoon with aeolian sediments. By the year 2018, the pine tree plantation area reduced to 3.25%, the dunefield area was 79.03%, and the extension of the degraded areas had increased and reached 17.71% of the total area. The pine tree plantation and the deforestation for conservation purposes are the main factors explaining the degradation of the dunefield during the period between 1948 and 2018, while regional climatic oscillations contributed as the secondary factor. Although internationally controversial, the present case study demonstrates that the removal of this exotic vegetation, through dune vegetation recovery programs, is often unsuccessful and may generate more degraded areas. However, in the case presented here, it was essential to remove the forest to ensure the dune field geodynamics and, therefore, the base (biotope) of the natural system (maintenance of the lagoon and the dunefield).

IMPACTOS DO DESMATAMENTO PROGRESSIVO DA AMAZÔNIA NA PRECIPITAÇÃO DO BRASIL

A Floresta Amazônica possui importância indispensável para o equilíbrio terrestre, pois proporciona diversos serviços ambientais. O desmatamento é uma ameaça imediata a este ecossistema, pois afeta os níveis de evapotranspiração da floresta, tornando o clima local mais quente e seco; podendo influenciar no clima além de seus limites, devido à circulação atmosférica. Este estudo avalia os efeitos de longo prazo do desmatamento progressivo da Amazônia sobre a precipitação no Brasil, através do modelo CCM3-IBIS. Os resultados encontrados mostraram anomalias negativas com maior intensidade nos meses de setembro, outubro e novembro afetando o regime de chuvas em grande parte das Regiões Norte e Centro-Oeste do Brasil. Já as anomalias anuais mostraram a influência da localização da floresta sobre as áreas que tiveram os índices pluviométricos reduzidos, em praticamente toda a Região Norte, leste da Região Nordeste e norte da Região Centro-Oeste. Além disso, os resultados de anomalias negativas anuais demonstraram que o impacto do desmatamento não é linear, pois no cenário de desmatamento total foram observadas anomalias negativas menos intensas que no cenário onde 60% da floresta foi transformada em pastagem. Em contrapartida, nas Regiões Sudeste e Sul prevaleceram as anomalias positivas de precipitação.

Pérdida de humedales y vegetación por urbanización en la cuenca del río Grijalva, México

La periurbanización se ha considerado como motor del cambio de uso del suelo y de la pérdida de ecosistemas y de biodiversidad. A partir de esta premisa, la investigación plantea el seguimiento, desde una doble perspectiva, histórica y predictiva, de los cambios en la superficie de los humedales y en la deforestación progresiva entorno a Villahermosa, la urbe más importante de la cuenca del río Grijalva, en el Estado de Tabasco (México). Se han utilizado diferentes métodos: el análisis bibliográfico para el periodo desde la fundación de la ciudad hasta el último tercio del siglo XX, la verificación de fotografías aéreas entre 1984 y 2008 y la modelización de escenarios futuros, entre 2020 y 2040. Desde el periodo colonial hasta mediados del siglo veinte, las inundaciones y la insalubridad dificultaron el crecimiento de la ciudad pese a la transformación de la red hídrica superficial en la cuenca, iniciada mediante la construcción de diques en el siglo XVII. Posteriormente, las elevadas tasas de pérdida de humedales y deforestación (-0.50 y -4.63 %) se incrementaron por la urbanización y el impacto de los programas de producción agropecuaria y petrolización. En los últimos 40 años, el desarrollo periurbano ocasionó la pérdida de 4.008 ha de vegetación arbórea y 289 ha de humedales, con una tendencia a desaparecer 1.449 y 356 ha adicionales respectivamente en el futuro 2040. Estos resultados resaltan la necesidad de rediseñar un programa metropolitano, transdisciplinario y sustentable que respete y actualice las reservas territoriales para regular la periurbanización.

Certificazione forestale in Calabria: attitudini, preferenze e disponibilità a pagare delle imprese di seconda trasformazione del legno

Abstract: Forest certification was born in the early 90s of the twentieth century in order to protect tropical and sub-tropical forests against a progressive deforestation and degradation. Forest certification is a valuable instrument for environmental protection and a useful tool of green marketing for forest-wood chain enterprises. In the last decades, in developed countries there has been increased consumer awareness of environmental protection and environmentally friendly wood products. This consumers’ attitude is related to the consumers’ willingness to pay a premium price for environmentally friendly wood products. In the international literature, some studies have investigated the consumers’ willingness to pay (WTP) for several certified wood products with different prices, while few studies have analyzed the willingness to pay of manufactures and enterprises of forest-wood chain for certified wood products. In addition, in the international literature there is a knowledge gap concerning the manufactures or consumers’ willingness to pay for local wood products compared to equivalent products from other geographical areas. Starting from these considerations, the main aims of this study are: (1) to analyze the wood manufactures’ willingness to pay a premium price for certified wood products; (2) to investigate the wood manufactures’ attitudes and willingness to pay for regional/local wood products. The study was conducted as part of the “Ambi.Tec.Fil.Legno” project involving 127 manufactures and enterprises of forest-wood chain located in Calabria region. At the end of the questionnaire survey, the information provided by 40 manufactures and enterprises of forest-wood chain were processed and analyzed (response rate 31.5%). The results show that the main factors that influence the purchase decisions of enterprises are the trust in the seller and the durability of the product. Concerning the manufactures’ willingness to pay for certified wood products, 40% of sample of manufactures is willing to pay a premium price with a mean value of 1.55%. A similar percentage of wood manufactures and enterprises (40%) are willing to pay a premium price to purchase local wood material with a mean value equal to 3.25%. The results of this study can support the decision makers in the definition of new strategies to enhance the forest sector in Calabria highlighting the potential benefits of forest certification and use of local wood at regional level.

Diagnosing nonlinearities in the local and remote responses to partial Amazon deforestation

AbstractUsing a set of fully coupled climate model simulations, the response to partial deforestation over the Amazon due to agricultural expansion has been analyzed. Three variations of 50% deforestation (all of western half, all of eastern half, and half of each grid box) were compared with total deforestation to determine the degree and character of nonlinearity of the climate response to partial deforestation. A metric is developed to quantify the degree and distribution of nonlinearity in the response, applicable to any variable. The metric also quantifies whether the response is saturating or accelerating, meaning significantly either more or less than 50% of the simulated response to total deforestation is attained at 50% deforestation. The spatial structure of the atmospheric response to Amazon deforestation reveals large areas across the tropics that exhibit a significant nonlinear component, particularly for temperature and geopotential height. Over the domain between 45°S and 45°N across all longitudes, 50% deforestation generally provides less than half of the total response to deforestation over oceans, indicating the marine portion of climate system is somewhat resilient to progressive deforestation. However, over continents there are both accelerating and saturating responses to 50% Amazon deforestation, and the response is different depending on whether the eastern or western half of Amazonia is deforested or half of the forest is removed uniformly across the region.

Multi-thread rivers in the Polish Carpathians: Occurrence, decline and possibilities of restoration

Multi-thread rivers are typified by the presence of interconnected channels separated by mid-channel bars or the islands forming as a result of vegetation encroachment on mid-channel bars. High gradients of channels and valley floors, high discharge variability, relatively low content of fine, cohesive sediments in the alluvial plain, coarse bed material and high sediment supply are environmental conditions that favour the development of braided channel pattern. Under natural conditions of the Holocene, island-braided channel pattern was typical of the rivers in the foreland of the Tatra Mountains and most likely also those draining the parts of the flysch Outer Carpathians underlain by thick-bedded sandstones complexes. These braided channels formed in the rivers flowing through mostly non-cohesive floodplains and fed with coarse-grained material exceeding competence of the rivers. Progressive deforestation of mountain catchments with the increasing area of cultivated hillslopes resulted in higher flood peaks and substantially increased sediment supply to river channels. Coupled with greater humidity of the final stages of the Little Ice Age, this led to the transformation of the island-braided rivers into bar-braided ones. Throughout the nineteenth century, the braided channel morphology expanded downstream to the foreland river reaches. In turn, over the twentieth century the braided morphology nearly disappeared from Polish Carpathian rivers, mostly as a result of their channelization. The effectiveness of these works was, however, strengthened by a decrease in sediment supply to the rivers caused by land use changes and by the reduced availability of bed material for fluvial transport resulting from in-channel gravel mining and partitioning of rivers with dam reservoirs. Environmental changes which have since occurred in the river catchments and disruption of the continuity of sediment transport by dams limit the feasibility of the restoration of braided channel pattern in Polish Carpathian rivers to their reaches supporting such morphology under natural conditions of the Holocene.

Deforestation causes different subregional effects on the Amazon bioclimatic equilibrium

AbstractDeforestation on Amazonia and central Brazil Cerrado could change regional climate, possibly shifting forest equilibrium into a bioclimatic envelope typical of savannas. Although impacts of climate change induced by deforestation are likely to vary subregionally, the potential geographic variation of these effects and the thresholds of rainforest and Cerrado removal that will affect Amazonian bioclimatic equilibrium remain unknown. We evaluate the effects of deforestation scenarios of increasing severity on the bioclimatic equilibrium of Amazon subregions. Results indicate that subregional precipitation responds in three distinct ways to progressive deforestation: a near‐constant rate of reduction, a rapid drop for low deforestation levels, and a decrease after intermediate deforestation levels. Additionally, while inner forest regions remain inside rainforest bioclimatic envelope, outer forest regions may cross forest‐savanna bioclimatic threshold even at low deforestation levels. We argue that at least 90% of Amazonia and 40% of Cerrado should be sustained to avoid subregional bioclimatic savannization.

Dinámica del cauce y de la llanura de inundación del río Ebro en el término de Alfaro

In this paper the author studies the dynamic of meandering channels of the river Ebro (section Rincón de Soto-Castejón). Afier working with aerial photography from 1927 to 1986 the most dynamic points have been chosen and their evolution has been analysed by a detailed cartography of the channel and the jloodplain. We have observed a progressive deforestation of the gro ves and a parallel occupation of the riverside by human action, which is revealed by the increase of cultivated areas and the development of dam works.

On the forest cover–water yield debate: from demand‐ to supply‐side thinking

Several major articles from the past decade and beyond conclude the impact of reforestation or afforestation on water yield is negative: additional forest cover will reduce and removing forests will raise downstream water availability. A second group of authors argue the opposite: planting additional forests should raise downstream water availability and intensify the hydrologic cycle. Obtaining supporting evidence for this second group of authors has been more difficult due to the larger scales at which the positive effects of forests on the water cycle may be seen. We argue that forest cover is inextricably linked to precipitation. Forest-driven evapotranspiration removed from a particular catchment contributes to the availability of atmospheric moisture vapor and its cross-continental transport, raising the likelihood of precipitation events and increasing water yield, in particular in continental interiors more distant from oceans. Seasonal relationships heighten the importance of this phenomenon. We review the arguments from different scales and perspectives. This clarifies the generally beneficial relationship between forest cover and the intensity of the hydrologic cycle. While evidence supports both sides of the argument – trees can reduce runoff at the small catchment scale – at larger scales, trees are more clearly linked to increased precipitation and water availability. Progressive deforestation, land conversion from forest to agriculture and urbanization have potentially negative consequences for global precipitation, prompting us to think of forest ecosystems as global public goods. Policy-making attempts to measure product water footprints, estimate the value of ecosystem services, promote afforestation, develop drought mitigation strategies and otherwise manage land use must consider the linkage of forests to the supply of precipitation.

Swidden Farming as an Agent of Environmental Change: Ecological Myth and Historical Reality in Indonesia

Abstract Swidden farming, once condemned as a major cause of deforestation, has increasingly come to be seen as a form of forest management and even conservation. Under traditional conditions, it is now assumed, swiddening was a sustainable practice and cultivation cycles were long enough to allow forest to regenerate during the fallow interval. This article tests these assumptions against historical evidence from Sulawesi (Indonesia) in the period 1820-1950. The data show that intensive bush-fallow swidden systems, with fallow periods of just five to six years, were already the norm in the early nineteenth century, when average population densities were still low and production for commerce limited. In most cases these traditional short-fallow systems were sustainable, in the sense of not entailing progressive deforestation beyond an established swidden-fallow complex. But within that complex the natural forest was permanently replaced by a much less rich and diverse anthropogenic vegetation. In some areas, moreover, swidden farming took an unsustainable, itinerant form involving the creation of fire-climax grassland. This too appears to have been a traditional pattern; there is no evidence that it resulted from population growth, or from external influences such as migration or commerce. The view of traditional swidden farming as an environmentally benign practice is an idealised one, and should not be allowed to obscure the fundamental incompatibility of agriculture with nature conservation.

Ecohydrology for a sustainable future in Africa – the cases of Ethiopia, Kenya and Tanzania

The productivity of some African lands has declined by 50% due to soil erosion and desertification over the period 2000–2010. Yield reductions may range from 2% to 40% (8% in average). This leads to increasing starvation of people, where only in Sub-Saharan Africa (SSA) the number of hungry people reached 212 million. In Ethiopia about 90% of arable lands is in mountainous areas, where live 90% of the human population and 60% of all livestock. The highlands exposed to improper agricultural practices has been heavily degraded in the last century. The country faces environmental challenges such as land degradation, limited quantity and quality of water resulting from progressive deforestation, improper agricultural practices and urbanization. Similar problems are touching other African countries, especially in the East Africa. To overcome these problems, efforts have been made to launch afforestation and conservation programs; however, success to date has been limited. Harmonization of ecohydrological principles with the existing efforts has been planned. The Gumera River basin has been chosen to be one of the ecohydrological demonstration sites. The Kenyan-Tanzanian border area is also an area of interest due to the large seasonal migrations of large mammals depending on water availability. Lake Naivasha in Kenya is used to demonstrate possible measures for restoration of land-water ecotone functions of Cyperus papyrus by restoration of hydrological regime in the tributaries deltas. This paper uses three cases to discuss the importance of ecohydrology for problem solving in Africa. Establishment of the regional centre for ecohydrology is being proposed.

2000 years of pastoralism and fire shaping high-altitude vegetation of Sierra de Gredos in central Spain

article i nfo The palynological record of Puerto de Serranillos provides insights into the late Holocene vegetation history of Sierra de Gredos in the Central Mountain System of the Iberian Peninsula. Overgrazing around the timberline has occurred at least throughout the past two millennia, related to the human management of the landscape. Before the 12th century AD, Pinus sylvestris forests were dominant with a diversity of accompanying trees and understorey. The current landscape of the Gredos Range is clearly anthropogenic, and includes a combination of forest patches, pastures, dense shrubby formations and prostrate junipers, overall generated during the transition between the 17th and 18th centuries AD, when continued human activity in the mountain pine forests, using fire and intensifying grazing practices, caused a progressive deforestation, and the expansion of the current fire-prone scrub.

The Holocene vegetation history of the Arfon Platform, North Wales, UK

Detailed pollen, charcoal and loss on ignition profiles were analysed from Llyn Cororion, North Wales, UK. The chronology was based on 11 radiocarbon dates. This site is particularly important for this region because its high‐resolution record improves the spatial and temporal resolution of records of Holocene vegetation change in an area characterized by a highly variable environment. An early Holocene phase of Juniperus‐Betula scrub was succeeded by Betula‐Corylus woodland. Quercus and Ulmus were established by c. 8600 14C yr BP, with Pinus dominating at c. 8430 14C yr BP. Local disturbance then allowed the spread of Alnus; Tilia was a common component of the forest by 5650 14C yr BP. Charcoal and pollen records suggest that by c. 2600 14C yr BP there was progressive deforestation, increased use of fire and spread of grassland; the first cereal grain was recorded at c. 2900 14C yr BP. Compared with data from upland Snowdonia, the results show that within a topographically diverse region there were significant local variations in forest composition. These variations developed as a response to interactions between many environmental parameters and were further complicated by the influence of human activity. In an area such as North Wales it is therefore unlikely that one site can be representative of regional Holocene vegetational development. The site is additionally important because it contributes to the data available for meta‐analyses of environmental change in the North Atlantic region, particularly as detailed pollen diagrams from coastal lake sites around western Europe are rare.

Fire and human activities on the Pyrenees mountain (Western Pyrenees and Eastern Pyrenees), inferred from pedoanthracological, palynological, micro-charcoal and archaeological data: An interdisciplinarity approach

In this communication we present new results about relation between fire, human activities and vegetation dynamics provided by interdisciplinary investigations carried out in the Palaeoenvironment and human activities on the Basque mountain program led by Galop since 2001 and in the Cerdagne’s program led by Rendu since 2002. This research field is located precisely in massif of Iraty (Western Pyrenees) and in the Enveig’s slope (Eastern Pyrenees). On the Basque mountain, macro-charcoal, micro-charcoal and pollen analysis show important phases of fire in relation to agro-sylvo-pastoral activities and confirm the use of slash and burns cultivation since Neolithic (Vanniere et al. 2001). These results fit well with palaeoenvironmental and archaeological data obtained in the same area. Strong human impact on the forest cover occurred during Bronze Age as it has been demonstrated by numerous contemporaneous burial mounds found and dated on the slopes (Marembert, 2000; Rendu, 2002; Carozza et al., 2005). Current landscape essentially consists of pastures with small stands of Fagus forest. Some isolated old oaks are principally situated near pastoral farms. Pedoanthracological analysis carried out in this area give informations about agro-pastoral activities and their consequences on Quercus – beech forest since Bronze Age period. Radiocarbon dated charcoals found in the slopes soils indicate fire. This induces clearance of the oak forest due to human activities. This progressive deforestation seems to have favoured Fagus expansion in the forest cover after 4000 BP. On the Enveig’s slope, the same interdisciplinarity approach shows a link between palaeoenvironment (Galop, 1998) and archaeological data (Rendu, 2003) and summer farming settlements. This revealed that occupation and grazing activities have started during Neolithic and have increased during Bronze Age period. Human impact appears to be the main factor for local extinction of Abies alba. It is interesting to compare micro-charcoal data and cumul dates of macro-charcoals to show that anthropic phases coincide with fire history both in Western and Eastern Pyrenees. This interdisciplinary approach helps in understanding the intensity of fires and their consequences on the dynamics of vegetation. Methodologicaly, pedoanthracoanalysis provide informations that confirm palynological and micro-charcoal results, with more precise spatial reconstructions. Laboratoire GEODE UMR5602, 5 allees A. Machado, Maison de la Recherche, 31058 Toulouse le Mirail cedex 9, France, Tel. : +33 (0)561 50 25 99, Fax : +33 (0)561 50 42 75, bal@univ-tlse2.fr. Laboratoire de Chrono-EcologieUMR 6565 CNRS – Universite de Franche-Comte 16 route de Gray 25030 Besancon cedex France, Tel. : +33 (0) 381 66 63 95, boris.vanniere@univ-fcomte.fr Laboratoire de Chrono-EcologieUMR 6565 CNRS – Universite de Franche-Comte 27, Chemin du Rayat, F-31600 MURET, France, Tel. : +33 (0) 561 50 25 99, Fax : +33 (0)561 50 42 75, didier.galop@univ-fcomte.fr. Laboratoire FRAMESPA, 5 allees A. Machado, Maison de la Recherche, 31058 Toulouse le Mirail cedex 9, France, Tel. : +33 (0) 561 50 36 77, christine.rendu@wanadoo.fr.

Agrarian change and diversity in the light of Brookfield, Boserup and Malthus: Historical illustrations from Sulawesi, Indonesia

This paper uses historical sources to examine the relationship between demography, econ- omy and ecology in three parts of the island of Sulawesi (Indonesia) over a long time period. Broadly speaking, these case studies suggest both the density of population and the intensity of agricultural activity at any given time and place were controlled by two factors. The first was the agricultural po- tential of the natural environment in terms of soil, climate and topography: populations were denser, and farming more area-intensive, in naturally fertile areas. The second was the extent to which the local economy was commercialised rather than subsistence-oriented: when commerce grew, so did both the population and the intensity of its farming systems. In terms of ecological sustainability and resilience, densely populated enclaves of intensive, commercialised agriculture tended to perform better than did sparsely populated and economically isolated areas of subsistence production, where progressive deforestation and land degradation sometimes occurred. Although one reason for this was simply that the former were located on better soils than the latter, other reasons included the greater use of tree crops, and the greater availability of labour for investment in what Brookfield called 'landesque capital', which characterised the more populous and commercialised areas.

Climatic and non-climatic effects on the δ 18O and δ 13C compositions of Lake Awassa, Ethiopia, during the last 6.5 ka

A comparison of a 6450 14C yr δ 18O and δ 13C record of authigenic calcite from Lake Awassa, Ethiopia, with other proxy climate records in the area suggests that the lake records long-term regional climate changes. Co-varying and increasing δ 18O and δ 13C values from ∼4800 BP suggest an aridification of climate after the early Holocene insolation maximum. After 4000 BP, humid conditions return until after ∼2800 BP when δ 18O increases again, reflecting more arid conditions recorded elsewhere in Ethiopia. In addition to these long-term changes, there are abrupt decreases in both δ 18O calcite and δ 13C calcite immediately after tephra layers. The likeliest explanation for these abrupt decreases in isotopes is the effect of tephra on the lake's catchment vegetation. δ 18O, δ 13C and lake-level measurements from Lake Awassa since the 1970s suggest that the lake is currently isotopically sensitive to short-term (annual–decadal) climate change. However, during this period, the catchment has undergone progressive deforestation that may have caused an increase in runoff. Caution is therefore required when reconstructing palaeoclimates as a contemporary lake may not always be a good analogue for lake hydrology in the past.

Effects of deforestation and reforestation on landscape spatial structure in boreal Saskatchewan, Canada

Monitoring landscape spatial structure has been recommended to detect degenerative trends in forest conditions, but such data have not been reported for boreal regions of North America under the influence of agricultural expansion. In this study, I analyzed the spatial characteristics of wooded area for several boreal landscapes in western Canada that exhibited persistent deforestation over approximately three decades prior to 1990. Patch area and perimeter metrics were quantified from topographic map chronosequences for the Halkett Lake, Mistatim, Debden and Bjorkdale areas of central Saskatchewan. The four landscapes varied from approximately 75–35% wooded and spanned a descending gradient in the proportion of the total area protected from land use change by federal or provincial legislation. Largest patch size and degree of coherence exhibited consistent temporal declines as deforestation proceeded within each landscape. When comparisons were made across the four landscapes within fixed time periods, largest patch size index and effective mesh size decreased as the proportion of land area wooded declined. A linear relationship with slope greater than unity was evident between the largest patch size index and the proportion of land area wooded for 1975/1976 ( r 2=0.99) and 1990 ( r 2=0.99). Metrics based on the size of the largest patch or the sum of squared patch sizes proved useful as baseline measures of landscape spatial structure. Number of patches, perimeter-to-area ratio, mean patch size and related metrics were less valuable as they exhibited variable responses with progressive deforestation. The temporal and spatial analyses yielded evidence that fragmentation exacerbated the effects of absolute wooded area losses. Deforestation disproportionately reduced the sizes of the largest patches, a finding with important management implications. Efforts to reverse deforestation within these landscapes should place priority on expanding large patches. Reforestation of agricultural lands has been proposed to offset carbon emissions from fossil fuel burning. Simulated reforestation with dispersed small patches resulted in little change in fragmentation as measured with landscape structure metrics. Simulated reforestation with larger blocks adjacent to existing large patches initiated reversal of the historic trends for largest patch size and degree of coherence. Increasing the size of provincial forests or protected areas, or restoring forest cover adjacent to them, would serve to expand the size of large forest patches. This reforestation strategy could provide supplementary benefits beyond carbon sequestration by reversing the degenerative process of fragmentation that has impaired forest wildlife and ecosystem processes.