Climate change has led to an increased occurrence of climate extremes. Drought is currently causing population declines in a wide range of species in rangelands. This interferes with the availability of feed for livestock. Grazing is thought to aggravate drought impacts, but there is a dearth of information on the combined effects of grazing and drought on the functional and taxonomic composition of the herbaceous vegetation in African savannas. Therefore, this study aimed to identify herbaceous species and plant functional types most susceptible to prolonged drought and grazing.

A six-year field experiment was performed in South Africa’s Limpopo province, combining drought and grazing treatments in a simulated DroughtAct experiment. This experiment evaluates ecosystem functions and services from grazed (G+) and ungrazed (G-) vegetation, under drought (D+) and non-drought (D-) conditions. Aboveground herbaceous biomass was harvested annually and separated into species. For all species, leaf traits were also recorded to describe their resource acquisition strategies. Generalized linear models were used to test for treatment effects and their interaction.

KEYWORDS: ANPP, drought, grazing, plant functional types

IPCC reports acknowledge that Africa will experience a higher level of warming than the global average. Methane has an 80-times greater warming potential than CO2, and accounts for 25% of the positive radiative forcing experienced by the lower atmosphere. Various CH4 sources have different isotopic signatures. Most assessments do not make use of isotopic information to detect sources and sinks of CH4, making this study a vital contribution to determining the drivers of the continued rise in CH4. Our research question therefore focuses on what are the concentrations, carbon isotopic ratios (⸹13C), and seasonal variations in isotopic signatures of the CH4 inputs to the air above the Wakkerstroom wetland and the Majuba Power Station? The objectives are 1) To measure carbon isotopic ratios in collected air samples from the Wakkerstroom wetland and the Majuba power station and deduce the isotopic source signatures for each source. 2) To plot CH4 mixing ratios as measured by TROPOMI to assess seasonal variations in CH4 concentrations. Methane gas samples were collected in 3L flexfoil bags. Stable isotope analysis of gas samples using high-precision continuous-flow gas chromatography/isotope-ratio mass spectrometry (GC-IRMS) was conducted, and the Keeling plot technique was used to determine the isotopic signature of each source. The y-intercept represents the source signature. The bias-corrected methane mixing ratio reported in parts per billion (ppb) was detected using the TROPOMI sentinel 5P satellite instrument. Results depict CH4 from the Wakkerstroom wetland as more depleted in carbon- 13 when compared to CH4 from the Majuba power station, which is carbon- 13 enriched. Furthermore, the Keeling plot technique was utilized to determine CH4 source signatures at the two sites. The Keeling plots revealed a source signature of – 56.6 ± 2.8 ‰ at the Wakkerstroom wetland and – 35.3 ± 1.0 ‰ at the Majuba power station. Satellite data using the TROPOMI indicates a continued surge in CH4 emissions with column concentrations of 1840 ppb at the Wakkerstroom wetland and 1860 ppb at the Majuba power station in 2022.

[Methane, Isotopic analysis, keeling plot, climate change, TROPOMI]

Climate change effects are accelerating at a worrying rate and will continue to be one of the frontline issues around sustainable livelihoods in Africa. Vulnerable rural communities dependent on rainfed agriculture face the harsh effects of climate change and are forced to be dependent on their local knowledge on subsistence farming and livestock production. The objective of this paper is to examine the effectiveness of local adaptation strategies using indigenous knowledge systems to cope with deleterious effects of climate change that have affected rural farmers for over four decades. The study adopts a mixed-methods approach with more bias on the qualitative methods like key informant interviews, focus group discussions, and life histories. The results from the study show that rural farmers struggle adopting mitigation strategies not locally led. Strategies like solar powered pumps for irrigation require capital that rural farmers do not possess. To build their resilience, households undertake a range of local led strategies such as homestead gardening, dry planting of drought resistant crops and more focus on small livestock like goats that can withstand high temperatures and less rainfall. Reliance on food aid and migration to neighboring countries proved not to be effective when exposed to other shocks like Covid-19. Thus, it came out that farmers have to rely on local knowledge, especially from the elderly who have managed to be food secure amid shocks presented to them.

[Climate change, adaptation, transformation, slow violence, local knowledge]