Biodiversity Impact Of Invasive Plants In Tropical Biodiversity Biology Essay

Biodiversity Impact Of Invasive Plants In Tropical Biodiversity Biology Essay Tropical zone is the biodiversity hot spot (Briggs, 1996) about three-quarters of the worlds species are confined to the tropic of the world (Wilson, 1992). Though tropical forest ecosystems are more resistant to invasion by alien plants than other biome (Edward, 2009), they are exceedingly threatening by invasive species (Association for Tropical Biology and Conservation, biotropica, 2010). Invasive species are creating significant challenges to the management and conservation of the indigenous biodiversity. The distribution of invasive plant species occurred at ecosystem level, community level and at the species level (Meyer et al., 2004). At least one exotic species is present in almost all tropical areas (Usher 1991). Invasive plants alter the local environment more favourable to them but less favourable to the native species (Hoffmann et al., 2004) and thus modified local ecosystem. Biological invasion has become a considerable economic, social, and particularly ecological problem of global impact (Cavalcante and Major, 2006). The important ecological impacts identified include reduction in native plant species richness, abundance and alternation in ecological function (Vitousek Walker, 1989; Adair Groves, 1998; Levine et al., 2003; Ogle, Reiners Gerow, 2003; Vila et al., 2006; Hejda, Pysek Jarosik, 2009 cited in Martin and Murray, 2010). Invasive plant species can covert the large area tropical vegetation to an exotic monoculture and greatly reduce the biodiversity, for example, the number of birds, mammals, tree seedlings were greatly reduced in Australia after the invasion of the area by alien plant species (Braithwaite et al. 1989) and Cogongrass (Imperata cylindrica) forms large, monotyp ic expanses, with Asia reporting over 35 million acres affected (Garrity et al. 1997). Invasive species are posing a serious threat to biodiversity (IUCN, 2000). The Millennium Ecosystem Assessment (2005) has pointed that the impacts of invasive species on the tropical ecosystems are increasing rapidly. Similarly, recognizing the increasing issue of impact of invasive species, Convention on Biological Diversity, call on contracting parties to prevent the introduction of, control or eradicate invasive species that threaten ecosystems, habitats and species Article 8 (h). This systematic review attempt to summarises, appraise and communicate the results  of the available studies to address the impact of invasive plants on tropical biodiversity. This protocol will provide a priori guide and allow scientific communities to comment on methodology and other relevant issues. Diverse studies are available related to impact of invasive plant species on tropical biodiversity. Some studies suggest that invasion of native vegetation by the non native plants does not always lead to decline in native biodiversity (e.g. Sax Gaines, 2003; Sax, Kinlan Smith, 2005). Biological invasions have been the subject of intensive ecological research during the last two decades (Fine 2001). Comprehensive studied have been done for many tropical forests e.g. the Hawaiian Islands (Fine, 2002) but some authors argues that the biological invasion research has generally ignored tropical forests ( Drake et al. 1989, Groves Burdon 1986, Williamson 1996 cited in Fine, 2002). In such contentious situation, it seems quite reasonable to syntheses these studies to improve the efficiency of the conservation efforts in preserving biodiversity of the tropics and develop a concrete evidence base on the impact of invasive species which will provide unbiased scientific evidence base to help decision-makers to decide and implement necessary policy intervention to stop further invasion of the tropical biodiversity and identify areas where evidence is lacking to direct research and funding on more crucial agendas. Objective of the review Primary question What are the effects of invasive plants on biodiversity of the tropical zone? Table 1: Definition of components of the primary systematic review question Subject Intervention Comparator Outcomes Biodiversity in the tropical zone Invasion by invasive plant species in tropical zone Biodiversity in forest, savannas or grassland before the invasion or any relevant or any relevant Any reported change in tropical biodiversity e.g. Species richness, abundance of native plant species, tree density Methods 3.1. Search Strategy Relevant published and unpublished literature and data will be collated by following strategy. Due to the resource constraints only English language literatures will be taken into consideration. 3.1.1 Scope of search I will use the following database search to retrieve the literatures and data ISI Web of Knowledge Science Direct Wiley InterScience Cambridge Journal Cab Direct CSA Biological Sciences Database (CSA/CIG)   BIOTROPICA In addition to grey literatures are searched in the website of relevant organization as listed in section 3.1.5 which helps to reveal important information about the tropical forestry and invasive species interaction. First searches are conducted on title, keyword and abstract basis and followed by full text searches. Hits are then checked for the relevance. 3.1.2 Search terms Effective and comprehensive list of related key words as described in the table -2 will be used to retrieve the literatures from the database specified above. Table 2: Search terms for review Subject term Intervention term combine with OR AND combine with OR Tropic* biodiversity Species richness Invas* plant non native plant exotic plant alien plant introduced plant Search term combinations Table: 3 Search term combinations and no of hits Key word 1 Key word 2 Total hits (Topic search) Refined hits in Web of science Tropic* biodiversity AND Invas* plant 54 Tropic* biodiversity AND Non native plant 32 Tropic* biodiversity AND exotic plant 74 Tropic* biodiversity AND alien plant 63 Tropic* biodiversity AND non-indigenous plant 07 Tropic* Species richness AND Invas* plant 38 Tropic* Species richness AND Non native plant 30 Tropic* Species richness AND exotic plant 60 Tropic* Species richness AND alien plant 34 Tropic* Species richness AND non-indigenous plant 04 tropical biodiversity AND (exotic plant) OR (invasive plant) OR(non native plant) OR (non indigenous plant) 7,109 425 No of hits and the retrieval of relevant literature varies between the data base searches, in the above table hits obtained by web of science is mentioned as an example. The same search tem combination give quite different hit in another database search, for example, for the first search term [tropic*biodiversity AND invas*plant] Cab direct retrieved 56 articles. In addition to the web of science the search databases mentioned in section 3.1.1 have been used in the preparation of this protocol and will also be used in final systematic review. 3.1.3 Specialist web sources will be conducted www.conservationevidence.com www.conserveOnline.org www.conservationevidence.org www.invasivespeciesinfo.gov 3.1.4. Internet Search The internet will be searched using the search engines. The first 70 hits for each search will be recorded and examined for relevance. www.google.com www.scholar.google.com www.scirus.com www.scientific.thomsonwebplus.com 3.1.5 Specialist agencies and organization data search At global level: Food and Agriculture Organization of the United Nations (FAO) IUCN/Invasive species specials group CABI- invasive species compendium Convention on biological diversity (CBD) International Weed Science Society (IWSS) UNEP-World Conservation Monitoring Centre (WCMC) Global Invasive Species Information Network (GISIN) Global Invasive Species Programme (GISP) In addition to this regional level agencies and organization in tropical countries will also consulted. Asia: Association of Southeast Asian Nations , Regional Centre for Biodiversity Conservation (ARCBC) Invasive Alien Flora of India Weed Science Society of Japan Weed Science Society of China Asia-Pacific Forest Invasive Species Network (APFISN Asia-Pacific Forest Invasive Species Network (APFISN) Australia: Invasive Species Council South America: Inter-American Biodiversity Information Network IABN Invasive Information Network 3.2. Study Inclusion criteria The relevant studies (articles, literatures, book sections) to be included in meta-analysis will be based in hierarchical judgment by first scanning the article titles followed by key words, abstracts and full text. The relevancy is determined by criteria as described below. If the data presented in the studies are not clear and needed to take more detailed description original authors and their respective organization will be contracted. Kappa analysis will be carried out for repeatability. Disputes between two reviewers will be solved by third independent reviewer. Geographical location: Study area of the relevant studies should be within the tropics (23.438 °S to 137 23.438 °N). 3.2.1. Relevant subjects: Any studies related to biodiversity changes in the tropical zone because of invasive plant species. 3.2.2. Types of intervention: Invasion of the tropical zone (forest land, agriculture land, grass land or savannas) by invasive plant species 3.2.3. Types of comparators: Any relevant studies and studies comparing the biodiversity of the tropical zone assessing before and after the effect of invasive plant species 3.2.4. Types of outcomes: Any study which shows biodiversity change (indicators like relative species richness or abundance) 3.2.5. Types of studies: Any study which describes qualitatively or quantitatively the effect of invasive plant species in the biodiversity (species richness, abundance) in forest land, grassland. Range land, agriculture land, savannas. Those studies which present comparison of before and after the invasion or the comparison of the proportion of exotic species to native species will be included. Studies can be articles in peer reviewed journals, book chapters or grey literatures 3.3. Potential effect modifier and reasons for heterogeneity Different edaphic, biotic, topographic and climatic condition which governs the vegetation type of the tropics such as soil quality, altitude, aspects, forest types and intensity of human disturbances which may respond to plant invasions in different ways affect the study outcomes. Furthermore, the biological characteristics of the invasive species also affect the study. 3.4. Study quality assessment The searched articles, grey literatures and documents will be assesses according to the previously designed study inclusion criteria. These are then checked independently for validity, reliability and applicability. A Quality assessment checklist is developed as shown below with the consultation of the review team and will be amended after stakeholders feedbacks. Internal and external validity will be checked using a set of criteria. Table 4: Quality assessment checklist for checking validity, reliability and applicability Variables Yes No 1 Target population and intervention defined 2 Sample representative 3 Experimental design/randomization 4 Base line information 5 Valid data collection 6 Description of confounding factors 7 Applicability of the research 8 Any biases Source: Adapted from class notes, 2010 and literature review 3.5. Data extraction strategy Qualitative and quantities information will be extracted from the studies included for the review. Information on invasive species, their effects on tropical biodiversity (species richness, abundance and competition) will be extracted in to a specially designed extraction form as shown in annex-1. Where data are available, data will be extracted as before and after data and other data will be extracted as appropriate. 3.6. Data synthesis and presentation Data synthesis method will be determined by the availability of the data and data type. The studies will be grouped according to the type of information available e.g. review article, original research. If sufficient quantitative information is available meta-analysis will be conducted to know the significance of the effect of invasive plant species to the tropical biodiversity. If in sufficient quantitative information is available qualitative analysis of evidence will be undertaken.