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Invasive species are considered to be a leading cause of the decline of threatened species. However, this view has been disputed because much of the evidence base is anecdotal. This systematic review, through an extensive, repeatable search using agreed selection criteria, examined the available scientific evidence on invasive species' interactions with the 1363 endangered and threatened species protected under the United States Endangered Species Act (ESA). The review found scientific evidence available for 116 endangered or threatened species (8.5% of the ESA list). Of these, 85 species (6.2%) were reported as being negatively impacted by invasive species: 39 located on the continental US and 39 on islands, with seven marine species. The relative percentages of species impacted differed according to location: 4.3% (n = 906) on the continental US, 9.3% (n = 420) on islands. It was found that predation by invasive vertebrates on birds on islands and competition between invasive plants and endangered or threatened plants on the mainland were the main mechanisms of impact. The results of this study contrast markedly with a previous study which found that 49% of imperilled species in the United States were threatened by invasive species. Further research is essential in order to evaluate the impact of invasive species on imperilled species on the ESA list; this would help to reduce the high degree of uncertainty regarding the threat of invasive species due to the lack of empirical information.

This Campbell systematic review examines the effects of input subsidies on agricultural productivity, beneficiary incomes and welfare, consumer welfare and wider economic growth. The review summarizes evidence from 15 experimental and quasi‐experimental studies and 16 studies that use computable models, the majority concerning sub‐Saharan Africa. This review examines studies that evaluate the impact of agricultural input subsidies, including subsidies for agricultural machinery, seeds or fertilisers, on farmers, farm households, wage labourers or food consumers in low‐ or lower‐ middle‐income countries. It includes 15 experimental and quasi‐experimental studies and 16 simulation modelling studies. The majority relate to sub‐Saharan Africa (15 to Malawi) and to subsidised fertilizers and seeds. Fertiliser and seed subsidies are associated with increased use of these inputs, higher agricultural yields and increased income among farm households, but evidence of their effects on poverty is limited. There is much evidence that subsidy schemes are prone to inefficiency, bias and corruption. Models show that introducing or increasing subsidies generally results in positive effects for consumers and wider economic growth. However, the models indicate that the way subsidies are funded, world input prices and beneficiary targeting all have important influences on predicted outcomes. The authors were not able to find any studies examining subsidies for machinery. Plain language summary Agricultural input subsidies raise input use, yields and farm income. The review in briefAgricultural input subsidies raise input use, yields and farm income, but the evidence base is small and comes from a limited number of schemes and countries. What is this review about?Greater use of improved seeds and inorganic fertilisers, and increased mechanisation, could boost agricultural productivity in some low‐ or lower‐middle‐income countries, but there is disagreement about whether subsidising these inputs is an effective way to stimulate their use.This review examines the evidence for impacts of input subsidies on agricultural productivity, beneficiary incomes and welfare, consumer welfare and wider economic growth. What are the main findings of this review?What studies are included?This review examines studies that evaluate the impact of agricultural input subsidies, including subsidies for agricultural machinery, seeds or fertilisers, on farmers, farm households, wage labourers or food consumers in low‐ or lower‐ middle‐income countries. It includes 15 experimental and quasi‐experimental studies and 16 simulation modelling studies. The majority relate to sub‐Saharan Africa (15 to Malawi) and to subsidised fertilizers and seeds.What are the main results of this review?Fertiliser and seed subsidies are associated with increased use of these inputs, higher agricultural yields and increased income among farm households, but evidence of their effects on poverty is limited. There is much evidence that subsidy schemes are prone to inefficiency, bia...

Background: Invasive species have been reported as one of the leading causes of species extinction. However, the evidence to support or contest their effects on the decline and/or extinction of threatened species has been largely unavailable and few efforts have been made to collate such information. In order to develop national and international policies addressing the loss of threatened species, and to prioritise research and mitigation efforts, the evidence needs to be systematically reviewed and mapped to determine the importance of such effects. Methods/design: The searching of online publication databases, grey literature and other resources, such as recovery plans of endangered species, aims to gather existing evidence on whether invasive species are a significant contributor to the decline and/or extinction of threatened species. This study focuses on US species under threat. The methods used to carry out the systematic review will address the following two fundamental questions: (a) what proportion of threatened species have an invasive species as a significant contributor to their decline and (b) through what mechanisms do invasive species contribute towards the decline of native species? The pool of resources gathered will be analysed for relevance and quality using a pre-defined scoring system. A systematic map will be produced, summarising information from individual studies. Where possible, data will be extracted from included studies and synthesised using meta-analysis.

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