Land use conversion from peat swamp forest to oil palm agriculture greatly modifies microclimate and soil conditions

Oil palm (Elaeis guineensis) agriculture is rapidly expanding and requires large areas of land in the tropics to meet the global demand for palm oil products. Land cover conversion of peat swamp forest to oil palm (large- and small-scale oil palm production) is likely to have negative impacts on microhabitat conditions. This study assessed the impact of peat swamp forest conversion to oil palm plantation on microclimate conditions and soil characteristics. The measurement of microclimate (air temperature, wind speed, light intensity and relative humidity) and soil characteristics (soil surface temperature, soil pH, soil moisture, and ground cover vegetation temperature) were compared at a peat swamp forest, smallholdings and a large-scale plantation. Results showed that the peat swamp forest was 1.5–2.3 °C cooler with significantly greater relative humidity, lower light intensities and wind speed compared to the smallholdings and large-scale plantations. Soil characteristics were also significantly different between the peat swamp forest and both types of oil palm plantations with lower soil pH, soil and ground cover vegetation surface temperatures and greater soil moisture in the peat swamp forest. These results suggest that peat swamp forests have greater ecosystem benefits compared to oil palm plantations with smallholdings agricultural approach as a promising management practice to improve microhabitat conditions. Our findings also justify the conservation of remaining peat swamp forest as it provides a refuge from harsh microclimatic conditions that characterize large plantations and smallholdings

Detecting Trends in Wetland Extent from MODIS Derived Soil Moisture Estimates

A soil wetness index for optical satellite images, the Transformed Wetness Index (TWI) is defined and evaluated against ground sampled soil moisture. Conceptually, TWI is formulated as a non-linear normalized difference index from orthogonalized vectors representing soil and water conditions, with the vegetation signal removed. Compared to 745 ground sites with in situ measured soil moisture, TWI has a globally estimated Random Mean Square Error of 14.0 (v/v expressed as percentage), which reduces to 8.5 for unbiased data. The temporal variation in soil moisture is significantly captured at 4 out of 10 stations, but also fails for 2 to 3 out of 10 stations. TWI is biased by different soil mineral compositions, dense vegetation and shadows, with the latter two most likely also causing the failure of TWI to capture soil moisture dynamics. Compared to soil moisture products from microwave brightness temperature data, TWI performs slightly worse, but has the advantages of not requiring ancillary data, higher spatial resolution and a relatively simple application. TWI has been used for wetland and peatland mapping in previously published studies but is presented in detail in this article, and then applied for detecting changes in soil moisture for selected tropical regions between 2001 and 2016. Sites with significant changes are compared to a published map of global tropical wetlands and peatlands

Nutrient removal processes in freshwater submersed macrophyte systems

A recent development for the control of eutrophication is the application of ecological engineering, involving designed wetlands for water treatment. The most undeveloped concept for designed wetlands is the use of submersed macrophytes. Apart from nutrient uptake, the macrophytes play a crucial role by creating a favourable environment for a variety of complex chemical, biological and physical processes that contribute to the removal and degradation of nutrients. In unharvested systems nitrogen is mainly removed by denitrification. If the system is harvested, nutrient assimilation is approximately of the same magnitude. Also, sedimentation of nitrogen is important, especially during colder periods when biological activity decreases. The removal of phosphorus is more dependent on biomass uptake and subsequent harvesting. Immobilisation by sorption and precipitation processes are also important removal mechanisms, especially in unharvested systems. The efficiency of the removal processes is largely determined by the Chemical and physical composition of the media. Much efficiency can be gained by tuning the composition and management of the plant according to the kind of water that is treated, thus creating favourable conditions for the different kind of removal processes

Is density flow balancing the salt budget of the Okavango Delta? Evidence from field and modeling studies

ABSTRACT In this paper, the salt balance of the Okavango Delta in Botswana is assessed. Large-scale arguments are presented that show the crucial role of the wetland/dryland interface for balancing the salt budget. On the other hand, modelling and field studies on selected islands are presented. Modelling results indicate a potentially unstable vertical concentration distribution below the islands. Results from TEM soundings and groundwater surveys clearly show strong conductivity anomalies for the islands. However, the data are still insufficient to prove the occurrence of density driven flow in the Okavango Delta

Do ecosystem services influence household wealth in rural Mali?

The impact of ecosystem services on human livelihood is rarely demonstrated. We investigated whether ecosystem services influence household wealth in semi-arid rural Mali, where climate variability and soil degradation were expected to regulate subsistence production. Mean rainfall, mean rain use efficiency, and rain use efficiency trends (a land degradation proxy) over the last 25 years were used to quantify ecosystem services. Asset wealth was measured in 2527 households from 65 villages spanning the range in ecosystem services. We evaluated effects on wealth, controlling for household size and demographics, ethnicity, village size, crop selection, and distance to open water and markets. While wealth variation was dominated by demographics, significant associations with ecosystem services were observed. Predicted household wealth increased significantly (20%) with rainfall. Effects of rain use efficiency mean and trends were also significant, but only when conditioned on rainfall. With lower rainfall, wealth increased with mean rain use efficiency (+ 33%) but decreased with rain use efficiency trend (? 22%). With higher rainfall, however, wealth decreased with rain use efficiency (? 57%) and increased markedly with rain use efficiency trend (+ 185%). While ecosystem services are clearly important, their effect on rural poverty is complex and potentially obscured by coping strategies that mitigate environmental limitations

Mapping of soil properties and land degradation risk in Africa using MODIS reflectance

AbstractThere is a need for up-to-date assessments and maps of soil properties and land health at scales relevant for decision-making and management, including for properties that are dynamic and hence change in response to management. Also, there is a need for approaches to soil mapping that capture the ever increasing effects that humans are having on the environment in general and specifically on soil properties worldwide. In this paper, we develop models for digital soil mapping based on remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) platform for Africa. The article presents maps of soil organic carbon (SOC), pH, sand and sum of exchangeable bases, as well as prevalence of root-depth restrictions in the upper 50cm of the soil profile. Prediction models were developed based on spatially balanced field survey data, representing all major climate zones on the continent. The prediction models for soil property mapping performed well, with overall RMSEP values of 10.6, 0.34, 9.1, and 6.5 for SOC, pH, sand, and sum of bases, respectively. The accuracy of the prediction model for root-depth restrictions was 77%, with an AUC of 0.85 and Cohen's kappa value of 0.52 when averaged across predictions run on independent test data. The methods and maps developed can provide much improved identification of soil and land health constraints, and spatial targeting of land management interventions at various scales, informing both policy and practice

Water flow dynamics in the Okavango river basin and delta - a prerequisite for the ecosystems of the delta

As part of the EU-funded project “Water and Ecosystem Resources in Regional Development––Balancing Societal Needs and Wants and Natural Resources Systems Sustainability in International River Basin Systems” (WERRD) (www.okavangochallenge.com), work is carried out aiming to improve and develop scientific methods that will facilitate the understanding of fluctuations of hydrological and ecosystem variables and likely human-induced trends concerning key characteristics of the Okavango River Basin in Southern Africa

The pan-Arctic catchment database (ARCADE)

The Arctic is rapidly changing. Outside the Arctic, large-sample catchment databases have transformed catchment science from focusing on local case studies to more systematic studies of watershed functioning. Here we present an integrated pan-ARctic CAtchments summary DatabasE (ARCADE) of >g 40g 000 catchments that drain into the Arctic Ocean and range in size from 1 to 3.1g ×g 106g km2. These watersheds, delineated at a 90g m resolution, are provided with 103 geospatial, environmental, climatic, and physiographic catchment properties. ARCADE is the first aggregated database of pan-Arctic river catchments that also includes numerous small watersheds at a high resolution. These small catchments are experiencing the greatest climatic warming while also storing large quantities of soil carbon in landscapes that are especially prone to degradation of permafrost (i.e., ice wedge polygon terrain) and associated hydrological regime shifts. ARCADE is a key step toward monitoring the pan-Arctic across scales and is publicly available: 10.34894/U9HSPV (Speetjens et al., 2022)