Vegetation dynamics in a corridor between protected areas after slash-and-burn cultivation in south-eastern Madagascar

International audienceSlash-and-burn cultivation is a major cause of deforestation in Madagascar, and abandonment leads to the secondary vegetation dynamics, i.e. colonization by herbaceous vegetation, shrubs and trees. The study was conducted in south-eastern Madagascar in a steep transition zone along an altitudinal and a sharp precipitation gradient between a high altitude rainforest and a lowland dry tropical forest. The restoration of gaps created by abandoned fields in this narrow, winding corridor could be essential to maintain connectivity between two areas (areas 1 and 2) of Andohahela National Park. Prior to imple- menting restoration, baseline ecological information is needed on the reference ecosystem and vegetation resilience must be studied to identify restoration needs. This study aims to (1) assess whether cultiva- tion practices (irrigated rice vs. cassava, maize and sweet potato) influence vegetation dynamics after abandonment; (2) study vegetation dynamics and soils over time since abandonment, and (3) compare secondary forest vegetation and soils with those of mature forest patches. Surveys of vegetation and soil were conducted in 26 secondary forest patches abandoned from 3 to >25 years (synchronic approach) and in 19 adjacent mature forest patches (controls). No relationship between age of abandonment and vege- tation species richness, composition or structure was found, but clear differences were detected between secondary and mature forest patches. Secondary forests are not colonized by species from mature forests, but instead their vegetation dynamics appear to lead to the establishment of thorny thickets dominated by Mimosa delicatula, which is absent from the mature forest

Vegetation dynamics in a corridor between protected areas after slash-and-burn cultivation in south-eastern Madagascar

a b s t r a c t Slash-and-burn cultivation is a major cause of deforestation in Madagascar, and abandonment leads to the secondary vegetation dynamics, i.e. colonization by herbaceous vegetation, shrubs and trees. The study was conducted in south-eastern Madagascar in a steep transition zone along an altitudinal and a sharp precipitation gradient between a high altitude rainforest and a lowland dry tropical forest. The restoration of gaps created by abandoned fields in this narrow, winding corridor could be essential to maintain connectivity between two areas (areas 1 and 2) of Andohahela National Park. Prior to implementing restoration, baseline ecological information is needed on the reference ecosystem and vegetation resilience must be studied to identify restoration needs. This study aims to (1) assess whether cultivation practices (irrigated rice vs. cassava, maize and sweet potato) influence vegetation dynamics after abandonment; (2) study vegetation dynamics and soils over time since abandonment, and (3) compare secondary forest vegetation and soils with those of mature forest patches. Surveys of vegetation and soil were conducted in 26 secondary forest patches abandoned from 3 to >25 years (synchronic approach) and in 19 adjacent mature forest patches (controls). No relationship between age of abandonment and vegetation species richness, composition or structure was found, but clear differences were detected between secondary and mature forest patches. Secondary forests are not colonized by species from mature forests, but instead their vegetation dynamics appear to lead to the establishment of thorny thickets dominated by Mimosa delicatula, which is absent from the mature forest

Antiproliferative cardenolides from <i style="">Pentopetia androsaemifolia </i>Decne.<i style=""> </i>from the Madagascar rain forest

248-257Plant natural products have historically been very important to drug discovery and development, particularly in the anticancer field. This is illustrated by a discussion of the structures and activities of camptothecin and its analogues, paclitaxel (Taxol®), the vinca alkaloids vinblastine and vincristine, and podophyllotoxin and its analogues. A description of the isolation of one new and three known cardenolides from the Madagascar plant Pentopetia androsaemifolia is then provided as an example of this approach to drug discovery. The paper concludes with a brief discussion of betulinic acid, an old compound which is being developed into an anticancer and anti-HIV agent, and ipomoeassin F, an interesting antiproliferative compound isolated from a plant collected in Suriname

Monitoring for outbreak associated excess mortality in an African city: Detection limits in Antananarivo, Madagascar

Objectives Quantitative estimates of the impact of infectious disease outbreaks are required to develop measured policy responses. In many low- and middle-income countries, inadequate surveillance and incompleteness of death registration are important barriers. Design Here, we characterize how large an impact on mortality would have to be to be detectable using the uniquely detailed mortality notification data from the city of Antananarivo, Madagascar, with application to a recent measles outbreak. Results The weekly mortality rate of children during the 2018–2019 measles outbreak was 161% above the expected value at its peak, and the signal can be detected earlier in children than in the general population. This approach to detecting anomalies from expected baseline mortality allows us to delineate the prevalence of COVID-19 at which excess mortality would be detectable with the existing death notification system in Antananarivo. Conclusions Given current age-specific estimates of the COVID-19 fatality ratio and the age structure of the population in Antananarivo, we estimate that as few as 11 deaths per week in the 60–70 years age group (corresponding to an infection rate of approximately 1%) would detectably exceed the baseline. Data from 2020 will undergo necessary processing and quality control in the coming months. Our results provide a baseline for interpreting this information

Excess mortality associated with the COVID-19 pandemic during the 2020 and 2021 waves in Antananarivo, Madagascar

Introduction COVID-19-associated mortality remains difficult to estimate in sub-Saharan Africa because of the lack of comprehensive systems of death registration. Based on death registers referring to the capital city of Madagascar, we sought to estimate the excess mortality during the COVID-19 pandemic and calculate the loss of life expectancy.Methods Death records between 2016 and 2021 were used to estimate weekly excess mortality during the pandemic period. To infer its synchrony with circulation of SARS-CoV-2, a cross-wavelet analysis was performed. Life expectancy loss due to the COVID-19 pandemic was calculated by projecting mortality rates using the Lee and Carter model and extrapolating the prepandemic trends (1990–2019). Differences in life expectancy at birth were disaggregated by cause of death.Results Peaks of excess mortality in 2020–21 were associated with waves of COVID-19. Estimates of all-cause excess mortality were 38.5 and 64.9 per 100 000 inhabitants in 2020 and 2021, respectively, with excess mortality reaching ≥50% over 6 weeks. In 2021, we quantified a drop of 0.8 and 1.0 years in the life expectancy for men and women, respectively attributable to increased risks of death beyond the age of 60 years.Conclusion We observed high excess mortality during the pandemic period, in particular around the peaks of SARS-CoV-2 circulation in Antananarivo. Our study highlights the need to implement death registration systems in low-income countries to document true toll of a pandemic