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.

马达加斯加在全新世晚期经历了环境变化，气候和人为驱动因素的相对重要性仍然是一个持续争论的主题。利用 Longiza 湖西南地区的古生态记录，我们提供了额外的记录，以阐明该岛的复杂历史，并确定晚全新世期间热带干燥森林中发生的变化。数据显示，直到公元 900 年，植被变化与气候变异相关，这反映在草、干旱适应类群、落叶乔木和同位素记录的变化中。从公元 980 年开始，由于从觅食转向畜牧业，导致生态系统进一步开放，人类活动的影响越来越大，表现为嗜粪孢子浓度增加。与此同时，区域古气候记录显示从公元 1000 年左右开始变得更加干燥，这可能加剧了植被结构的变化。如木炭和孢子记录中的多个峰值所示，该地区周围增加使用火和食草动物可能会维持更开放的植被。自公元 1900 年以来，西南地区的花粉记录表明，随着草、先锋类群的丰度增加和多样性的减少，生态系统变得越来越开放，这与气候和农牧业活动的同时影响有关。我们的研究表明，在过去的千年里，公元 950 年左右的干旱条件开始以草为主的群落取代森林为主的植被，目前被描述为一个开放的生态系统。