Biodiversity in rubber agroforests

Jungle rubber tuinen zijn extensieve rubber agroforests die qua structuur op secundaire bossen lijken, en waarin wilde soorten door de boer worden getolereerd. Met het verdwijnen van het laaglandregenwoud rijst de vraag of de begroeiing die ervoor in de plaats komt een aantal kenmerken en functies van het oorspronkelijke bos kan behouden. Dit proefschrift is een evaluatie van de rol van rubber (Hevea brasiliensis) agroforests in het behoud van soorten van het laaglandregenwoud in Sumatra. Primair bos en rubberplantages dienden als referentiesystemen voor biodiversiteits- en rubberproductie-waarden. De rubberplantages bestonden voornamelijk uit rubberbomen (98% van de bomen), terwijl het percentage rubberbomen in de jungle rubber agroforests gemiddeld slechts 41% was. Nieuwe biodiversiteitsgegevens over terrestrische en epifytische pteridofyten werden verzameld, en vergeleken met bestaande gegevens over bomen en vogels. De leeftijd van de jungle rubber proefvlakken varieerde van 9 tot 74 jaar, terwijl de leeftijd van de proefvlakken in rubberplantages 5 tot 19 jaar was. In de ondergroei van jungle rubber werd een redelijk aantal 'bossoorten' wordt gevonden, en verscheidene soorten terrestrische pteridofyten kunnen als indicatorsoorten voor bosverstoring en regeneratie van het bos gebruikt worden. Hoewel het behoud van soorten in jungle rubber door het beheer en door een herbeplantingscyclus van ongeveer 40 jaar wordt beperkt, draagt dit bosachtige landgebruik bij aan de soortenrijkdom in een verarmd landschap dat steeds meer door monocultuurplantages gedomineerd wordt. Oudere jungle rubber agroforests hebben een grotere natuurwaarde, maar zijn meestal minder productief voor de boer.

Terrestrial pteridophytes as indicators of a forest-like environment in rubber production systems in the lowlands of Jambi, Sumatra

Species richness of terrestrial ferns and fern allies (Pteridophyta) may indicate forest habitat quality, as analysed here for a tropical lowland area in Sumatra. A total of 51 standard 0.16 ha plots in primary forest, rubber (Hevea brasiliensis) agroforests and rubber plantations was compared for plot level diversity (average number of species per plot) and landscape level diversity (species-area curves). Average plot level species richness (I I species) was not significantly different amongst the three land use types. However at the landscape level the species-area curve for rubber agroforests (also called jungle rubber) had a significantly higher slope parameter than the curve for rubber plantations, indicating higher beta diversity in jungle rubber as compared to rubber plantations. Plot level species richness is thus not fully indicative of the (relative) richness of a land use type at the landscape scale because scaling relations differ between land use types. Terrestrial fern species can serve as indicators of disturbance or forest quality as many species show clear habitat differentiation with regard to light conditions and/or humidity. To assess forest habitat quality in rubber production systems as compared to primary forest, terrestrial pteridophyte species were grouped according to their ecological requirements into 'forest species' and 'non-forest species'. Species-area curves based on 'forest species' alone show that the understorey environment of jungle rubber supports intermediate numbers of 'forest species' and is much more forest-like than that of rubber plantations, but less than primary forest. Species richness alone, without a priori ecological knowledge of the species involved, did not provide this information. Jungle rubber systems can play a role in conservation of part of the primary rain forest species, especially in areas where the primary forest has already disappeared. In places where primary forest is gone, jungle rubber can conserve part of the primary forest species, but large areas of jungle rubber are needed. In places where primary forest is still present, priority should be given to conservation of remaining primary forest patches. (C) 2004 Elsevier B.V. All rights reserved

RANUNCULUS-HEDERACEUS L AS INDICATOR OF LAND-USE CHANGES IN THE NETHERLANDS

In The Netherlands Ranunculus hederaceus is a rare species that occurs in running waters. It appears to be confined to zones with a constant supply of mineral-poor groundwater, originating from highly fertilized fields. The relation between species performance and chemical composition of the water was investigated by means of response analysis. No relation was found unless the mineral content of the water was multiplied with stream velocity (yielding a measure for mineral supply per time unit). In the latter case significant correlations were found for calcium, bicarbonate, sodium, chloride and sulphate. We discuss whether low P-availability in the system could limit biomass production of Ranunculus hederaceus, although this appeared to be unlikely, Competition for light with algae and large helophytes is more likely to be a major reason for the absence of the species in stagnant waters. The situation near Oudemolen illustrates the indicative value of the species. Detailed investigations showed that artificial drainage changed the original mesotrophic conditions into eutrophic circumstances, which are much more favourable for this species. Hence, the increase of a rare plant species like Ranunculus hederaceus does not always indicate the well-being of a nature reserve

Biofuel plantations on forested lands: Double jeopardy for biodiversity and climate

The growing demand for biofuels is promoting the expansion of a number of agricultural commodities, including oil palm (Elaeis guineensis). Oil-palm plantations cover over 13 million ha, primarily in Southeast Asia, where they have directly or indirectly replaced tropical rainforest. We explored the impact of the spread of oil-palm plantations on greenhouse gas emission and biodiversity. We assessed changes in carbon stocks with changing land use and compared this with the amount of fossil-fuel carbon emission avoided through its replacement by biofuel carbon. We estimated it would take between 75 and 93 years for the carbon emissions saved through use of biofuel to compensate for the carbon lost through forest conversion, depending on how the forest was cleared. If the original habitat was peatland, carbon balance would take more than 600 years. Conversely, planting oil palms on degraded grassland would lead to a net removal of carbon within 10 years. These estimates have associated uncertainty, but their magnitude and relative proportions seem credible. We carried out a meta-analysis of published faunal studies that compared forest with oil palm. We found that plantations supported species-poor communities containing few forest species. Because no published data on flora were available, we present results from our sampling of plants in oil palm and forest plots in Indonesia. Although the species richness of pteridophytes was higher in plantations, they held few forest species. Trees, lianas, epiphytic orchids, and indigenous palms were wholly absent from oil-palm plantations. The majority of individual plants and animals in oil-palm plantations belonged to a small number of generalist species of low conservation concern. As countries strive to meet obligations to reduce carbon emissions under one international agreement (Kyoto Protocol), they may not only fail to meet their obligations under another (Convention on Biological Diversity) but may actually hasten global climate change. Reducing deforestation is likely to represent a more effective climate-change mitigation strategy than converting forest for biofuel production, and it may help nations meet their international commitments to reduce biodiversity loss