Pollen records of the 14th and 20th centuries AD from Lake Tsizavatsy in southwest Madagascar

Razanatsoa, Estelle; Gillson, Lindsey; Virah‐Sawmy, Malika; Woodborne, Stephan

doi:10.1201/9781003162766-20

Cited by 3 publications

(10 citation statements)

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“…In the east, massive forest clearing occurred around AD 700-1100 (Agarwal et al, 2005). A similar gradual change in the structure of the ecosystem toward more open vegetation was recorded in the savanna woodland at Lake Tsizavatsy (Razanatsoa et al, 2021a). These suggest that although the climate initially affected the change in the vegetation as evidenced by an increase in grass and a decrease in riverine and dry forest tree taxa, it was maintained by human activities by the change in subsistence from foraging to pastoralism as indicated by the increase in herbivory and fire activities at least until AD 1600.…”

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearssupporting

confidence: 57%

“…These records demonstrate a wetter period from AD 1300 until AD 1500, which coincides with the relatively wet period in the northwest record during the 500-year the dry phase (Scroxton et al, 2017). The tree isotope records demonstrated a significant trend in decreasing rainfall over time (Razanatsoa, 2019), which also became more pronounced in the last millennia as recorded in pollen records from the region (Burney, 1993;Razanatsoa, 2019;Razanatsoa et al, 2021a;Virah-Sawmy et al, 2016). Although pollen evidence from the region generally supports climate as a long-term driver of vegetation change (Virah-Sawmy et al, 2016), evidence of climate change is equivocal and difficult to assess due to complex interactions with anthropogenic factors.…”

Section: Introductionsupporting

confidence: 56%

“…Such presence, however, has not affected the ecosystem surrounding Lake Longiza, similar to the changes recorded at Tsizavatsy which is located further south where the only forager communities in southwest Madagascar live. Palaeoecological data from their region suggested that foraging activities alone did not lead to massive changes in the vegetation (Razanatsoa et al, 2021a). Instead, it was the combination of these practices (such as pastoralism) and drying of the area that led to the opening of the ecosystem (Razanatsoa et al, 2021a;2021b).…”

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearsmentioning

confidence: 99%

“…Palaeoecological data from their region suggested that foraging activities alone did not lead to massive changes in the vegetation (Razanatsoa et al, 2021a). Instead, it was the combination of these practices (such as pastoralism) and drying of the area that led to the opening of the ecosystem (Razanatsoa et al, 2021a;2021b). The findings from Lake Longiza suggest the presence of earlier communities in the region practiced foraging activities starting around AD 600 until the end of the first millennium AD and that occurred while a recovery of dry forest trees was This suggests that at least until AD 900, the vegetation responded solely to climate variation.…”

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearsmentioning

confidence: 99%

“…This mosaic landscape reflects the biologically and physically heterogeneous nature of the modern landscape in southwest Madagascar (Callmander et al, 2013;Cornet and Guillaumet, 1976;Du Puy and Moat, 1996;Grubb, 2003;Moat and Smith, 2007;World Wildlife Fund [WWF], 2001) that facilitates a diverse array of taxa (Kindvall, 1996;Oliver et al, 2015;Watt, 1947). Such a record of vegetation alongside charcoal, dung fungal spores and existing regional climate records (Razanatsoa, 2019;Razanatsoa et al, 2021a;Scroxton et al, 2017) allows us to investigate the response of the tropical dry forest during the Late-Holocene to rainfall variability and landuse from fire and pastoralism.…”

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearsmentioning

confidence: 99%

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Synergy between climate and human land-use maintained open vegetation in southwest Madagascar over the last millennium

et al. 2021

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Madagascar experienced environmental change during the Late-Holocene, and the relative importance of climatic and anthropogenic drivers is still the subject of an ongoing debate. Using palaeoecological records from the southwest region at Lake Longiza, we provide additional records to elucidate the complex history of the island and to identify the changes that occurred in the tropical dry forest during the Late-Holocene. The data showed vegetation changes associated with climate variability until AD 900 as reflected by the variation in grass, dry-adapted taxa, deciduous trees, and isotope records. An increasing effect of human activities was recorded, indicated by increased coprophilous spore concentration, as a result of a shift from foraging to pastoralism leading to further opening of the ecosystem from AD 980. At the same time, the regional palaeoclimate record showed drier conditions from around AD 1000, which could have accentuated the changes in vegetation structure. More open vegetation was likely maintained by increased use of fire and herbivory around the area, as indicated by the multiple peaks in the charcoal and spore records. Since AD 1900, the pollen record from the southwest region showed that the ecosystem became increasingly open with an increased abundance of grass, pioneer taxa, and reduced diversity, which was linked to a simultaneous effect of climate and agropastoralism activities. Our study suggests that the dry conditions around AD 950 initiated the replacement of forest-dominant vegetation with grass-dominant communities over the last millennium, depicted as an open ecosystem at present. Subsequent changes in subsistence activities would have further maintained an open-structured ecosystem.

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Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearssupporting

confidence: 57%

Section: Introductionsupporting

confidence: 56%

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearsmentioning

confidence: 99%

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearsmentioning

confidence: 99%

Section: Vegetation Change Fire History and Herbivory In Southwest Madagascar During The Last 2000 Yearsmentioning

confidence: 99%

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Synergy between climate and human land-use maintained open vegetation in southwest Madagascar over the last millennium

et al. 2021

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Modern pollen rain reveals differences across forests, open and mosaic landscapes in Madagascar

Razafimanantsoa,

Razanatsoa

2024

Plants People Planet

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Societal Impact StatementPalaeoecological investigations are crucial in understanding millennial to centennial land use and land cover change. By analysing the modern pollen rain from four main vegetation types across Madagascar, this research provides baselines for improving the interpretation of pollen records in palaeoecological studies. This study determines the modern pollen‐vegetation relationship in Madagascar and gives a better understanding of the island's landscapes. Despite some spatial limitations, this approach contributes to resolving the debated topic related to the origin of Madagascar's open ecosystems. Knowing the vegetation history prior to and after human settlement would help guide biodiversity management and its associated ecosystem services.Summary Modern pollen rain contributes to calibrating and defining palaeo‐records relative to the current vegetation of diverse landscapes. Quantifying past vegetation change is important to better frame sustainable and resilient management methods of biodiversity considering human needs. In this paper, we aim to assess modern pollen assemblages in different vegetation types in Madagascar and inform how these could contribute to the interpretation of palaeo‐records. We identified modern pollen assemblages from 21 samples across four major vegetation types in Madagascar, including seven (N = 7) newly generated samples from the tropical dry forest in the Northwest region and 14 datasets downloaded from the African Pollen Database website. The downloaded datasets are from core tops representing modern vegetation previously analysed in the tropical dry forests and spiny thickets, the wooded grassland–bushland mosaic and the littoral humid forest. We evaluated the frequency of different taxa in the samples and conducted multivariate analyses to evaluate the similarities and ecological affinities between samples. Pollen rain reflected the main vegetation types across Madagascar and provided information on the current structure and state of the landscape. Regarding the interpretation of pollen records, pollen rain samples revealed that: (i) Open mosaic ecosystems should contain a percentage of at least 40% grass pollen, informing on the origin of the vegetation in older samples and the state of degradation in more recent vegetation reconstructions; and (ii) Anthropogenic vegetation such as plantations are marked by the abundance of pioneer taxa such as Pinus and/or Eucalyptus spp. with a frequency >20%. Our findings improve the interpretations of pollen records and help differentiate past distribution of forest, open and mosaic vegetation, in Madagascar. It will contribute to further research on human practices, land use and into scenarios of conservation planning not only in Madagascar but also across the tropics.

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The role of palaeoecology in reconciling biodiversity conservation, livelihoods and carbon storage in Madagascar

Gillson,

Razanatsoa,

Razafimanantsoa

et al. 2023

Front. Conserv. Sci.

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Planting trees is proposed as an important climate mitigation tool, but can be detrimental to biodiversity and livelihoods if not carefully planned and managed, with landscape history and livelihoods in mind. In Madagascar, deforestation is of concern, and a threat to forest-adapted biota. However, much of Madagascar’s landscape harbours ancient mosaic and open ecosystems that are home to unique suites of flora and fauna and provide a wide range of ecosystem services. Though guidelines for ecologically and socially responsible reforestation are emerging, the potential role of landscape history and palaeoecology has been generally underemphasised. Here, using Madagascar as a case study, we argue that forest restoration projects need a sound understanding of landscape history that includes a greater integration of palaeoecological data. This would help establish the former composition and extent of forests and also investigate the antiquity of open and mosaic ecosystems. When economic interests are strong, information from palaeoecology and environmental history can help reduce biases when identifying appropriate locations and suites of species for forestation. Furthermore, a reflective approach to landscape history can contribute to restoration projects that integrate cultural and livelihood considerations. A transdisciplinary approach that considers local needs and cultural context can facilitate the design and implementation of restoration projects that share benefits equitably. Underpinning this ambition is a more comprehensive consideration of ecosystem service benefits in a changing climate that includes accurate carbon storage calculations, as well as other ecosystem services including water provision, soil formation and erosion prevention, grazing resources, medicine and cultural components.

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Pollen records of the 14th and 20th centuries AD from Lake Tsizavatsy in southwest Madagascar

Cited by 3 publications

References 0 publications

Synergy between climate and human land-use maintained open vegetation in southwest Madagascar over the last millennium

Synergy between climate and human land-use maintained open vegetation in southwest Madagascar over the last millennium

Modern pollen rain reveals differences across forests, open and mosaic landscapes in Madagascar

The role of palaeoecology in reconciling biodiversity conservation, livelihoods and carbon storage in Madagascar

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