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Improving the Carbon Balance of Cattle Grazing Systems in Madagascar

By Ravaka Minoarisoa Randriambololona, Alexis Heritiana Randrianiaina, Marc Spiekermann, and Harifidy Rakoto Ratsimba

Climate change is a global issue having significant effects on the grazing systems in Madagascar. In the Boeny region, extensive cattle farming based on natural grazing is at risk of forage shortages. Working with stakeholders across the system, this research assessed the vulnerability and adaptive potential of farms by studying farmers’ preferences, carbon (C) sources and C-stock positions, resource flows, and system management methods.

Livestock farming plays an important role in Madagascar’s cultural, social and economic life. Nearly 70% of Malagasy households and 75% of rural households are involved in raising livestock. Cattle farming predominates, with 85% of households managing the Malagasy zebus breed across the northwest, the west coast, and the extreme south of the island (MinEL, 2015). In the northwest, the Boeny Region accounts for over 35% of the cattle herd. Extensive, natural grazing systems are most prevalent in the region. However, the impacts of climate change are affecting the sustainability of these grazing systems. A lack of fodder during the dry season, coupled with frequent bush fires to compensate for the needs of herds, are obstacles to the region’s agricultural development.

The goal of this research was to assess the relationship between different grazing systems and climate change in the Boeny region. The specific objectives were to: (i) assess the vulnerability of the different grazing systems to climate change, (ii) evaluate and map the system’s contribution to climate change through the development of C assessments while determining the source and sink positions of GHGs at the pasture system level.

Study description
Soil sampling and farmer interviews were conducted in Boeny region within the four communes of Antanambao Andranolava, Belobaka, Katsepy, and Tsaramandroso in (Fig. 1).

Figure 1. Location of study area in the Boeny region of Madagascar.

The adopted methodology follows the concept of climate-related impacts and risk developed by the IPCC AR5 (GIZ and EURAC, 2017), which explains the interactions between components of risk, hazard, vulnerability, exposure, and adaptation measures. The assessment of the grazing system’s contribution to climate change was evaluated through its C balance, soil organic C (SOC) stock (by Loss of Ignition method), and methane emissions attributable to livestock, which were analyzed and modeled to determine the impact of various management scenarios.

Soil organic carbon and pasture improvement
The results focus on cattle farming associated with improved forage grazing areas, which represent a high potential for soil C storage. Soils sampled to the 30 cm depth under under traditional pasture composed by Hyparrhenia spp. and Aristida spp. had significantly less C mass (36 +/- 11.05 t ha-1) than soils under improved pasture (55 +/- 9.45 t ha-1) (Fig. 2). This difference in C storage is associated with the partial introduction of other forage species (mainly Brachiaria and Stylosanthes sp.) that can generate more biomass and contribute to a GHG emissions offset and a positive C balance. In our case, the grazing system composed of 96.2% native pasture with a moderately degraded pasture management regime and 3.8% improved forage species resulted in a positive C balance of 28.43 t CO2 eq yr-1 between 2022 and 2023 (Fig. 2).

Figure 2. Soil organic carbon and pasture type (left) and the carbon balance resulting from partial introduction of improved forage species between 2022 and 2023 (right).

Modeling scenarios of inaction
Climate change and the practice of bush clearing by fire are the major factors leading to the gradual degradation of native pastures and are major risks to increasingly negative C balances predicted by modeling analysis—equaling -3.15 t CO2 eq ha-1 yr-1 by 2030, -6.46 t CO2 eq ha-1 yr-1 by 2050, and -26.96 t CO2 eq ha-1 yr-1 by 2080, if no mitigating actions are implemented (Fig. 3).

Figure 3. Model predictions of the future impact of current grazing lands in Boeny, Madagascar.

Modeling scenarios linked to an increase in improved forage crop area
By understanding the performance of alternative forage species, it is possible to optimize agricultural practices for more efficient C sequestration and sustainable livestock production. According to the model scenario analysis, an increase of 2 to 10% per year in improved forage crop area is projected to lead to a net increase in respective increases in C sequestration of 26.03 to 46.77 t CO2 eq ha-1 yr-1 up to 2030 (Fig. 4).

Figure 4. Scenario for increasing the area with improved forage crop establishment, Boeny, Madagascar.

By comparison, the analysis by Fisher et al. (1994) of C stored by pastures introduced to the South American savanna shows that Stylosanthes capitata stocked 71.1 t C ha-1 and Brachiaria humidicola stocked 76.0 t C ha-1 in the 0–20 cm layer soil depth. These results are higher than the amount of soil C stocked in our study. This former analysis was done under grass-based pastures, which made a striking contribution to Oxisol’s soil C compared to the Ferruginous soils (Latosols) dominating the Boeny Region. However, the C values for degraded pastures under Ferruginous soils in Brazil are quite similar to those calculated in our study, averaging 14.3 g C kg-1 soil (Vendrame et al., 2010). Furthermore, our study highlights a significant difference between the amount of C in soils under improved and traditional pastures. These results concur with those of the study by Fisher et al. (1994), which also revealed a significant difference between soil C stock under conventionally cultivated soil and under a cropping system with permanent plant cover of Stylosanthes capitata and Brachiaria humidicola.

Our study also shows that cattle farming has the particularity of being able to offset GHG emissions through C storage associated with the C stocks of native savannas and improved forage species, despite relatively low performance. An earlier study confirms this feature of cattle farming, in which the C balance remains positive in the grazing system despite emissions from enteric fermentation (Dolle et al., 2013). Also, the study made by Fisher et al. (1994) could account for the sequestration of 100-507 Mt yr-1 estimated at 35 M ha, which is a higher amount than our study. Another study (Tennigkeit and Wilkes, 2008), showed that with different management of the grazing system the C-fixation potential linked to the forage crop can vary from -12.1-46.5 t CO2 eq ha-1 yr-1, which is quite similar to our study.

Results from (Ravaloniaina, 2023) indicate that Brachiaria brizantha cv. Marandu produces more biomass compared to the current highland pastures, at 2.55 +/- 0.92 and 1.91 +/- 0.55 t DM ha-1, respectively. Similarly, this species provides feed with higher N content (64.08Å} 2.98 g crude protein DM kg-1) and greater ingestibility (96.22 +/- 15.4 g DM kg-1 live weight 0.75) compared to the current pasture feed (60.09 +/- 3.99 g crude protein kg-1 DM and 79.14 +/- 20.4 g DM kg-1 live weight 0.75).

Forage species, mainly Brachiaria and Stylosanthes sp., have a high C-fixing potential but their establishment must be appropriately managed to avoid a net increase in GHG emissions (Tennigkeit and Wilkes, 2008). Therefore, it is recommended to encourage the sustainable adoption of improved grazing lands, but with adequate technical support and financial incentives to facilitate the transition. This action would prevent or reduce the frequency of native pasture expansion through bush burning, increase soil biomass sequestration and enhance the density of local forage species (GIEC, 2002). At the same time, such examples of improved practice provide decision-makers with evidence-based grazing system management procedures to guide future policy for more resilient agricultural development.

Summary
Improved management of grazing lands is critical for increased forage production and increased soil C storage. Integrating Brachiaria and Stylosanthes forage grasses and preventing burning was predicted to substantially increase the balance of rangelands on the Beony region of Madagascar. Policy, technical support and financial incentives are essential in supporting the adoption of climate-smart pasture management practices.

Acknowledgement
This article is adapted from LLANDDEV (Land Landscape Development Research Lab). 2023. Etude d’impact des cultures fourragères sur le bilan carbone des systèmes de pâturage de bovins dans la région Boeny. This paper has been produced with the financial support of the European Union (EU) and the GIZ (Deutsche Gesellschaft für Internationale Zusammenarbeit GmbH). Its contents are the sole responsibility of the authors and do not necessarily reflect the views of the EU or GIZ.

Ing. Randriambololona is Researcher, LLANDDEV, University of Antananarivo, Madagascar, e-mail: minsravaka@gmail.com. Mr. Randrianiaina is Technical Advisor at GIZ. Mr. Spiekermann is responsible for knowledge management on the PROSOL project. Dr. Ratsimba is Principal Researcher, LLANDDEV.

Cite this article
Randriambololona, R.M., Randrianiaina, A.H., Spiekermann, M., Ratsimba, H.R. 2024. Impact of Forage Crops on the Carbon Balance of Cattle Grazing Systems in Madagascar, Growing Africa 3(1), 12-15. https://doi.org/10.55693/ga31.GWXQ8189

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