Scientific consensus is building that we have entered a new era of mega species extinction, with current rates of extinction at least three orders of magnitude more than background. In late 2012 the International Union for Conservation of Nature Red List14of Threatened Species included 65,518 species, of which 20,219 are threatened with extinction with 795 already extinct. This categorization included a recent assessment of Madagascar’s unique palms which found that a staggering 159 species of the total of 192 are threatened with extinction. Export of indigenous palm seeds is becoming an important export market for NWFPs and is a contributory threat factor for some species.
Through the Global Trees campaign and under the auspices of IU_N’s Species Survival _ommission certain plant groups and regions have been partially or fully recently assessed for their conservation status including conifers (Coniferae), cycads (families Boweniaceae, Cycadaceae and Zamiaceae), Magnoliaceae, maples (Acer spp.), oaks (Quercus spp.), palms (Arecaceae), rhododendrons (Rhododendron spp.); and central Asia, Guatemala, Ethiopia and Eritrea, Mexican cloud forests. However, most families and genera comprising mainly tree and woody species have yet to be subjected to comprehensive assessments of their level of endangeredness, which will help inform where conservation effort and resources are best directed.
An assessment of conservation status of tree species in Guatemala found little correspondence between earlier assessments with suggestions that tree species data and information in and outside of the country may have been a factor in earlier discrepancies (Vivero et al. 2006). The new assessment identified 79 endangered tree species in Guatemala including 10 critically endangered endemics. Approximately 60% of the 762 tree species in 85 botanical families in the floristically rich, and replete with endemics, cloud forests of Mexico were assessed as threatened (González-Espinosa et al. 2011). Central Asian forests and woodlands are under severe threat from over-exploitation, desertification, pests and diseases, overgrazing and fires. A combination of factors including the cessation of subsidized timber from the former Soviet Union, rural poverty, a lack of alternative energy sources and the lack of institutional capacity to protect and regulate forests have all added to the pressure on vulnerable forests of the region (Eastwood et al. 2009). Of 96 tree taxa assessed in Central Asia, including Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan, 46% (or 44 of them) were found to be threatened with extinction in the wild. The preliminary assessment of 428 endemic and near endemic woody plants in Ethiopia and Eritrea determined that 135 species (including 31 trees) were threatened (Vivero et al. 2011).
Of the 151 species assessed in the family Magnoliceae, approximately 74% (or 112 species) have been found to be threatened (Cicuzza et al. 2007). Approximately 45% of Quercus species are considered endangered (or 79 out of 176) for which data was available and sufficient for assessment (Oldfield and Eastwood 2007). The conservation status of 125 species of maple trees (123 Acer spp. and 2 Dipteronia spp.) has been assessed with at least 54 taxa (28% of maple taxa) found to be threatened (Gibbs and Chen 2009). Of the approximately 1018 known Rhododendron species, mainly woody shrubs, approximately 25% (or 316 species) have been found to be threatened (Gibbs et al. 2011).
Developed countries with greater available Government resources, but often less species diversity, sometimes maintain their own Red lists. Sweden, for example, maintains its own Red List which includes European ash (Fraxinus excelsior), broad-leaved lime (Tilia platyphyllos), wych elm (Ulmus glabra), European white elm (U. laevis) and field elm (U. minor): the main threats coming from exotic diseases (Sweden p 18 and 20). More often than not, threat assessments for tree species in developing countries are lacking due to a shortage of trained botanists and conservation biologists and supporting resources for field surveys. Currently available threat assessments where these have been undertaken, are typically several too many years old and are in need of updating. The taxonomic assessment of many tropical tree genera, including those with important FGR, such as ebony (Diospyros), mangoes (Mangifera), Syzygium and Terminalia, is often incomplete. Furthermore, updated taxonomic information and botanical keys may not be readily available in the countries where the species naturally occur. The Global Tree Specialist Group, part of the IUCN-Species Survival Commission has identified major challenges for conservation of individual tree species. They estimate that approximately 8,000 tree species are threatened with extinction, with about 1,000 tree species critically endangered and likely to go extinct unless urgent action is taken (Oldfield et al. 2008; Global Trees Campaign http://www.globaltrees.org/about.htm). Of threats to the 52 endangered tree species profiled at the Global Trees website, and covering different plant families and geographic regions, the main threats were from overharvesting (37%), followed by biological factors including naturally rare and restricted (23%), habitat loss and conversion (21%), fire and overgrazing (13%) and climate change and invasives (6%), but many species are threatened by a combination of threat factors and their interaction. These data are from a small sample (about 5 % of threatened tree species) and overharvesting is likely to be overrepresented due to deep concerns about precious timber tree species. Overharvesting, including poorly regulated, unregulated and illegal harvesting, is arguably the most currently important threat factor for FGR, because this activity causes a loss of genetic diversity and populations on those tree species which have most economic value and utility. Over the next century, climate change and interactions with other threats will be become the most important threat for tree species and populations. Thomas et al. (2004) have shown through modelling that between 18-35% of the world’s animal and plant species are on the path or committed to extinction due to climate change, and this figure is not taking into account interactions with other threats; these authors have also shown that the climate change threat to survival of species is much greater than from habitat loss, but varies depending of the biome under consideration.
18.104.22.168 Loss of Intraspecific diversity
The loss of intraspecific diversity in economically important tree species has been a major concern of the forestry profession for many decades. Despite the many continuing and longer-term threats to FGR a high, but variable, level of success has been achieved for conserving and utilizing the genetic diversity of many commercially important tree species for timber and paper pulp production. This has often been achieved under the auspices of tree breeding programs in developed countries, and for which there are many examples, and increasingly led by private sector consortia. Similarly there has been vital genetic resources work undertaken in the developing tropics by national agencies for some major topical timber and NWFP species. This has usually been done with international, support including national donor funded projects and agencies operating in international mode; e.g. teak (Tectona grandis), gmelina (Gmelina arborea) and neem (Azadirachta indica), assisted by FAO and Danida Forest Tree Seed Centre, many African ATPs species assisted by ICRAF; big-leaf mahogany (Swietenia macrophylla) through CATIE; tropical American pines supported by CAMCORE, and chukrasia (Chukrasia tabularis) and beach sheoak (Casuarina equisetifolia) supported by ACIAR and CSIRO Australian Tree Seed Centre.
The main threats to intraspecific diversity in tree species are essentially the same as those which cause species extinction (see 22.214.171.124). The loss of entire populations or genetically distinctive provenances (for species exhibiting clinal variation) has both short and long term adverse consequences. The short term consequences include potential major changes to ecosystem function and services for native forests in which they occur through to loss of documented seed sources of known performance. The longer term consequences are that loss of populations is a well-identified pre-cursor for species extinction, and loss of vital genetic material for selection and tree improvement programs. For trees introduced into a new environment with a broad genetic base, better adapted land races may often evolve in a small number of generations, but the same is not true for recovery of lost diversity. A study on red pine (Pinus resinosa) has indicated that very long time periods, possibly on scales of tens of thousands of years, are required for long-lived, long-generation organisms like trees to recover genetic diversity following a genetic bottleneck and loss of diversity (Mosseler et al. 1992).
Major losses to diversity have also occurred for high value species which have been selectively and most heavily harvested both for their timber and for NWFPs – paradoxically this has meant that some of the most economically useful tree species have been the most genetically denuded. This has consequences not only for immediate seed supply for replanting, but also the limited genetic diversity, often with only lower quality or less desirable phenotypes remaining, reduces the opportunities for selection and breeding. Cornelius et al. (2005) have assessed the maximum negative dysgenic response to a single selective logging-mediated phenotypic selection event in big-leaf mahogany (Swietenia macrophylla) to be small, i.e. ≤5%, and rather insignificant, but for different species with more heritable traits (e.g. chemotypes) and/or several to many cycles of selection of superior phenotypes then dysgenic selection is more problematic.
Below are listed just some examples, from around the globe, of the many hundreds of valuable tree species which have already lost, or are at imminent risk of losing important intraspecific diversity:
Frankincense (Boswellia papyrifera) – an economically important NWFP tree in Ethiopia and Eritrea but which is rapidly declining and predicted to be commercially extinct within the next 15-20 years. The causes of decline are related to resin tapping which reduces reproductive and recruitment potential (Rikers et al. 2006; Eshete et al. 2012). Trees dying from attack by long-horned beetles and other causes are failing to be replaced through seedling recruitment due to excessive firing and increased grazing pressures (Groenendijk et al. 2012). Forest reduction and degradation and competition for land use have also been identified as threatening factors (Ethiopia p 15).
Thailand rosewood (Dalbergia cochinchinensis) – intraspecific variability is highly threatened (Thailand p 52), and this species has been heavily and selectively overharvested throughout its natural range in Cambodia, Laos, Thailand and Vietnam and continues to be cut, often illegally. Good seed sources from native stands are scarce, as surviving populations are reduced to scattered and isolated trees of poor phenotypes.
Melanesian whitewood (Endospermum medullosum) – the fastest-growing trees originate from east and south-east Santo in Vanuatu (Vutilolo et al. 2005), but these populations have almost disappeared due to land use change, absence of regeneration in coconut plantations and cattle properties, and harvesting of remnant trees (Corrigan et al. 2000; Vanuatu).
Chi ye cai (Erythrophleum fordii) is a valuable timber tree threatened by overexploitation, which in China now only occurs in small, fragmented and degraded stands and with greatly diminished genetic diversity (China p 18).
Shining gum (Eucalyptus nitens) – the mountain-top populations in northern NSW, Australia which have shown potential for timber production in South Africa are committed to extinction from climate change.
Euphrates poplar (Populus euphratica); and Tana River poplar (Populus ilicifolia) – fast-growing, multipurpose riparian trees from the Middle East, Central Asia and China, and Kenya, respectively, with a remarkable range of tolerance to edaphic and climatic extremes, but declining and endangered throughout its range by clearance, overharvesting, and modification to hydrological regimes (Viart 1988, Ball et al. 1996, Cao et al. 2012).
African cherry (Prunus africana) – bark harvested for use in treatment of benign prostatic hypertrophy. The species has been CITES listed (Appendix II) since 1995 but almost all native populations of this keystone afromontane species in central, eastern and southern Africa are threatened by overharvesting which often kills trees, and also from land use and climate changes. In Republic of South Africa close monitoring and controls may provide a greater level of protection than other parts of its range (Republic of South Africa p 45). Populations of P. africana on Madagascar are morphologically distinct and likely constitute a different taxon, are similarly threatened but no longer exported due to previous overharvesting (Madagascar p 22).
Pterocarpus santalinus (red sandalwood) -this highly valuable timber and NWFP timber species from Andhra Pradesh State in India has been overharvested especially during the 1950s and 1960s. The species was CITES Appendix II listed in 1995, but an illegal smuggling trade continues with concern for loss of genetic diversity (MacLachlan and Gasson 2010; India p 63).
Swietenia mahogani (West Indies mahogany) – native to the Caribbean Islands and southern tip of Florida (USA). This is the most valuable mahogany timber producing species and has been commercially exploited for more than five hundred years: the small residual populations are thought to have undergone dysgenic selection (Styles 1972). Dysgenic selection is most likely if successive regeneration cycles are derived from only a small residual number of poor quality phenotypes (Ledig 1992), but whether this has occurred for this species is now difficult to determine. Hybridization with other Swietenia species, such as with S. macrophylla on Cuba, is another threat to the species genetic integrity and resources.
Santalum sp. (Western Province sandalwood) – An undescribed species of sandalwood exists in three small populations, each consisting of only a few individuals, in coastal areas of Western Province, Papua New Guinea. This sandalwood, referred in literature to as S. macgregorii, has been shown to have highly fragrant heartwood with high santalol content (Brophy et al. 2009), but is at high risk of being harvested which would cause the species to go extinct as there is no natural regeneration or ex situ conservation actions.
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