International audience | The strong pest pressure on intensive banana cultivation in the French West Indies led to the intensive use of chlordecone (an organochlorine insecticide) between 1972 and 1993. Due to its high toxicity for the population and the environment, many studies were conducted on the transfer of chlordecone over the last 20 years. However, most studies focused on the dissolved fraction of chlordecone, while the particle-bound fraction was understudied. Therefore, this study reconstructs pluri-decadal erosion rates ( 1980–2023) and associated chlordecone particle-bound transfers from soil and sediment cores sampled in a cultivated headwater catchment (Saint-Esprit, Martinique). Based on sediment accumulation analyses in an agricultural reservoir, high erosion rates ( 10 t ha−1 yr−1) were found in the investigated catchment during the study period, with values exceeding the estimated tolerable soil loss rate in tropical contexts ( 2.2 t ha−1 yr−1). Based on the analysis of soil cores sampled along a banana plantation hillslope, this study highlights the formation of colluvial deposits with high levels of chlordecone contamination. When these areas are affected by erosion processes, this leads to massive remobilization of particle-bound chlordecone to water bodies. Indeed, in sediment sampled in the downstream reservoir, we observed a drastic increase in these transfers since 2006, synchronous with changes in agricultural practices. This study therefore highlighted the occurrence of legacy contamination at toeslope positions, which was estimated to potentially persist for 4000 to 11,000 years. Such a residence time highlights the need to implement changes in land management to effectively reduce erosion of agricultural soils, particularly in areas identified as ”temporary deposition zones” for chlordecone contamination, in order to protect downstream water bodies from chlordecone transfer. To achieve this, agricultural practices that may increase soil erosion, such as herbicide application or intensive ploughing, should be minimized. Overall, this study improved our understanding of erosion and associated chlordecone transfers in tropical environments.

The strong pest pressure on intensive banana cultivation in the French West Indies led to the intensive use of chlordecone (an organochlorine insecticide) between 1972 and 1993. Due to its high toxicity for the population and the environment, many studies were conducted on the transfer of chlordecone over the last 20 years. However, most studies focused on the dissolved fraction of chlordecone, while the particle-bound fraction was understudied. Therefore, this study reconstructs pluri-decadal erosion rates ( 1980–2023) and associated chlordecone particle-bound transfers from soil and sediment cores sampled in a cultivated headwater catchment (Saint-Esprit, Martinique). Based on sediment accumulation analyses in an agricultural reservoir, high erosion rates ( 10 t ha−1 yr−1) were found in the investigated catchment during the study period, with values exceeding the estimated tolerable soil loss rate in tropical contexts ( 2.2 t ha−1 yr−1). Based on the analysis of soil cores sampled along a banana plantation hillslope, this study highlights the formation of colluvial deposits with high levels of chlordecone contamination. When these areas are affected by erosion processes, this leads to massive remobilization of particle-bound chlordecone to water bodies. Indeed, in sediment sampled in the downstream reservoir, we observed a drastic increase in these transfers since 2006, synchronous with changes in agricultural practices. This study therefore highlighted the occurrence of legacy contamination at toeslope positions, which was estimated to potentially persist for 4000 to 11,000 years. Such a residence time highlights the need to implement changes in land management to effectively reduce erosion of agricultural soils, particularly in areas identified as ”temporary deposition zones” for chlordecone contamination, in order to protect downstream water bodies from chlordecone transfer. To achieve this, agricultural practices that may increase soil erosion, such as herbicide application or intensive ploughing, should be minimized. Overall, this study improved our understanding of erosion and associated chlordecone transfers in tropical environments.

International audience | To create more resilient cities, it is important that we understand the effects of the global change drivers in cities. Biodiversity-based ecological indicators (EIs) can be used for this, as biodiversity is the basis of ecosystem structure, composition, and function. In previous studies, lichens have been used as EIs to monitor the effects of global change drivers in an urban context, but only in single-city studies. Thus, we currently do not understand how lichens are affected by drivers that work on a broader scale. Therefore, our aim was to quantify the variance in lichen biodiversity-based metrics (taxonomic and trait-based) that can be explained by environmental drivers working on a broad spatial scale, in an urban context where local drivers are superimposed. To this end, we performed an unprecedented effort to sample epiphytic lichens in 219 green spaces across a continental gradient from Portugal to Estonia. Twenty-six broad-scale drivers were retrieved, including air pollution and bio-climatic variables, and their dimensionality reduced by means of a principal component analysis (PCA). Thirty-eight lichen metrics were then modelled against the scores of the first two axes of each PCA, and their variance partitioned into pollution and climate components. For the first time, we determined that 15% of the metric variance was explained by broad-scale drivers, with broad-scale air pollution showing more importance than climate across the majority of metrics. Taxonomic metrics were better explained by air pollution, as expected, while climate did not surpass air pollution in any of the trait-based metric groups. Consequently, 85% of the metric variance was shown to occur at the local scale. This suggests that further work is necessary to decipher the effects of climate change. Furthermore, although drivers working within cities are prevailing, both spatial scales must be considered simultaneously if we are to use lichens as EIs in cities at continental to global scales.

To create more resilient cities, it is important that we understand the effects of the global change drivers in cities. Biodiversity-based ecological indicators (EIs) can be used for this, as biodiversity is the basis of ecosystem structure, composition, and function. In previous studies, lichens have been used as EIs to monitor the effects of global change drivers in an urban context, but only in single-city studies. Thus, we currently do not understand how lichens are affected by drivers that work on a broader scale. Therefore, our aim was to quantify the variance in lichen biodiversity-based metrics (taxonomic and trait-based) that can be explained by environmental drivers working on a broad spatial scale, in an urban context where local drivers are superimposed. To this end, we performed an unprecedented effort to sample epiphytic lichens in 219 green spaces across a continental gradient from Portugal to Estonia. Twenty-six broad-scale drivers were retrieved, including air pollution and bio-climatic variables, and their dimensionality reduced by means of a principal component analysis (PCA). Thirty-eight lichen metrics were then modelled against the scores of the first two axes of each PCA, and their variance partitioned into pollution and climate components. For the first time, we determined that 15% of the metric variance was explained by broad-scale drivers, with broad-scale air pollution showing more importance than climate across the majority of metrics. Taxonomic metrics were better explained by air pollution, as expected, while climate did not surpass air pollution in any of the trait-based metric groups. Consequently, 85% of the metric variance was shown to occur at the local scale. This suggests that further work is necessary to decipher the effects of climate change. Furthermore, although drivers working within cities are prevailing, both spatial scales must be considered simultaneously if we are to use lichens as EIs in cities at continental to global scales. | info:eu-repo/semantics/publishedVersion