DOI: 10.5061/dryad.q2bvq83q2
title: Data from: Grazing herbivores reduce herbaceous biomass and fire activity across African savannas

description: Fire and herbivory interact to alter ecosystems and carbon cycling. In
 savannas, herbivores can reduce fire activity by removing grass biomass,
 but the size of these effects and what regulates them remain uncertain. To
 examine grazing effects on fuels and fire regimes across African savannas,
 we combined data from herbivore exclosure experiments with remotely sensed
 data on fire activity and herbivore density. We show that, broadly across
 African savannas, grazing herbivores substantially reduce both herbaceous
 biomass and fire activity. The size of these effects was strongly
 associated with grazing herbivore densities and, surprisingly, was mostly
 consistent across different environments. A one-zebra increase in
 herbivore biomass density (~100 kg/km2 of metabolic biomass) resulted in a
 ~53 kg/ha reduction in standing herbaceous biomass and a ~0.43 percentage
 point reduction in burned area. Our results indicate that fire models can
 be improved by incorporating grazing effects on grass biomass.
description: # Grazing herbivores reduce herbaceous biomass and fire activity across
 African savannas --- ## Authors A. Tyler Karp* Sally I. Koerner, Gareth P.
 Hempson Joel O. Abraham T. Michael Anderson William J. Bond Deron E.
 Burkepile Elizabeth N. Fillion Jacob R. Goheen Jennifer A. Guyton Tyler R
 Kartzinel Duncan M. Kimuyu Neha Mohanbabu Todd M. Palmer Lauren M.
 Porensky Rob M. Pringle Mark E. Ritchie Melinda D. Smith Dave I. Thompson
 Truman P. Young A. Carla Staver *Corresponding Author: A. Tyler Karp
 Institutions: Yale University and Brown University ## ABSTRACT Fire and
 herbivory interact to alter ecosystems and carbon cycling. In savannas,
 herbivores can reduce fire activity by removing grass biomass, but the
 size of these effects and what regulates them remain uncertain. To examine
 grazing effects on fuels and fire regimes across African savannas, we
 combined data from herbivore exclosure experiments with remotely sensed
 data on fire activity and herbivore density. We show that, broadly across
 African savannas, grazing herbivores substantially reduce both herbaceous
 biomass and fire activity. The size of these effects was strongly
 associated with grazing herbivore densities and, surprisingly, was mostly
 consistent across different environments. A one-zebra increase in
 herbivore biomass density (~100 kg/km2 of metabolic biomass) resulted in a
 ~53 kg/ha reduction in standing herbaceous biomass and a ~0.43 percentage
 point reduction in burned area. Our results indicate that fire models can
 be improved by incorporating grazing effects on grass biomass. ##
 Description of the data and file structure ### dataset_1:
 exclusion.herbaceous.biomass.data.ecol.letters.final.csv *park=unique ID
 for park or reserve  *plot=unique ID for experiment exclosure plot
 *date=date or year sample collected *previous.year.rainfall=annual
 rainfall from the previous year of the biomass measurement (mm/yr)
 *rainfall..mm.yr.=annual rainfall from the year of the biomass measurement
 (mm/yr) *percent.sand=percent sand in soil (%) *fire.frequency=frequency
 that the plot burned (1/yr) *years.since.experiment.start= months since
 experiment start (years) *biomass.measurement.type=method of measuring
 herbaceous biomass in the plot *herbaceous.biomass.kg.ha.=herbaceous
 biomass in the exclusion plot (kg/ha)
 *control.herbaceous.biomass.kg.ha=herbaceous biomass in the control plot
 (kg/ha) *deltaG=difference in herbaceous Biomass between the exclusion and
 the control (deltaG = exclusion-control) (kg/ha) *deltaG/Gcontrol=ratio of
 the difference in herbaceous Biomass in the exclusion and control over the
 control (deltaG/Gcontrol)(kg/ha) *weighted.ave.body.size=average body size
 of grazer and mixed feeders weighted by density. Elephants are excluded.
 Partial exclosures have NA values (kg) *proportion.nonruminant=proportion
 of non-ruminant grazer and mixed feeders. Elephants are excluded. Partial
 exclosures have NA values *grazer+mf sum (lovegrove)_ex = metabolic
 density of grazers and mixed feeders (kg^b/kg^2) excluded from plot;
 calculated using b=0.899 for wildlife and 0.75 for cattle; After Staver et
 al. (2021) *grazer+mf sum (lovegrove)_present = metabolic density of
 grazers and mixed feeders (kg^b/kg^2) present in plot; calculated using
 b=0.899 for wildlife (Lovegrove, 2000) and 0.75 for livestock (Kleiber,
 1932) ; After Staver et al. (2021) *grazer+mf/2 sum (lovegrove)_ex =
 metabolic density of grazers and 1/2 of mixed feeders (kg^b/kg^2) excluded
 from plot; calculated using b=0.899 for wildlife and 0.75 for cattle;
 After Staver et al. (2021) *grazer+mf/2 sum (lovegrove)_present =
 metabolic density of grazers and 1/2 of mixed feeders (kg^b/kg^2) present
 in plot; calculated using b=0.899 for wildlife (Lovegrove, 2000) and 0.75
 for livestock (Kleiber, 1932) ; After Staver et al. (2021) *grazer+mf sum
 (order)_ex = metabolic density of grazers and mixed feeders (kg^b/kg^2)
 excluded from plot; calculated using b= order level average from (Genoud
 et al. 2018) *grazer+mf sum (order)_present= metabolic density of grazers
 and mixed feeders (kg^b/kg^2) present in plot; calculated using b= order
 level average from (Genoud et al. 2018) *grazer+mf/2 sum (order)_ex =
 metabolic density of grazers and 1/2 of mixed feeders (kg^b/kg^2) excluded
 from plot; calculated using b= order level average from (Genoud et al.
 2018) *grazer+mf/2 sum (order)_present= metabolic density of grazers and
 1/2 of mixed feeders (kg^b/kg^2) present in plot; calculated using b=
 order level average from (Genoud et al. 2018) *grazer+mf sum (species)_ex=
 metabolic density of grazers and mixed feeders (kg^b/kg^2) excluded from
 plot; calculated using b= species level average when avaible from (Genoud
 et al. 2018) *grazer+mf sum (species)_present = metabolic density of
 grazers and mixed feeders (kg^b/kg^2) present in plot; calculated using b=
 species level average when avaible from (Genoud et al. 2018) *grazer+mf.2
 sum (species)_ex= metabolic density of grazers and 1/2 of mixed feeders
 (kg^b/kg^2) excluded from plot; calculated using b= species level average
 when avaible from (Genoud et al. 2018) *grazer+mf/2 sum (species)_present
 = metabolic density of grazers and 1/2 of mixed feeders (kg^b/kg^2)
 present in plot; calculated using b= species level average when avaible
 from (Genoud et al. 2018) *DMI_order = Dry Matter intake (kg/ha); Using
 metabolic biomass (b=order level; MF0.5) calculated after Staver et al.
 (2021) using equation from Dong et al. (2006). ### HEX_code_publication.R
 Code to analyze herbaceous biomass and exclusion experiment data and to
 create figures 2, 3, 4, 6. Figures were modified for aesthetics in adobe
 illustrator. ### dataset_2:
 burned.area.reserve.data.ecol.letters.final.csv *reserve=name of reserve
 *country=name of country reserve is located in *sand=sand content (average
 for the reserve) (g/kg) *seasonality=Average number of months 70% of
 annual precip falls in (average for reserve)(number of months)
 *mean.annual.rainfall=mean annual rainfall (average for reserve)(mm.yr)
 *tree.cover=tree cover (average for reserve)(%) *mean.burned.area=mean
 annual burned area (average for reserve)(%)
 *max.potential.burned.area=maximum potential annual burned area (average
 for reserve)(%) *detaBA=difference in max.potential.burned.area and
 mean.burned.area (average for reserve)(percentage points)
 *detaBA/BApotential=proportion of difference in max.potential.burned.area
 and mean.burned.area over the max.potential.burned.area (average for
 reserve)(%) *lov_density_ave.g.mf =metabolic density of grazers and mixed
 feeders (kg^b/kg^2); calculated using b=0.899 for wildlife and 0.75 for
 cattle; After Staver et al. (2021) *order_density_ave.g.mf= metabolic
 density of grazers and mixed feeders (kg^b/kg^2); calculated using b=
 order level average from (Genoud et al. 2018) *species_density_ave.g.mf =
 metabolic density of grazers and mixed feeders (kg^b/kg^2); calculated
 using b= species level average when avaible from (Genoud et al. 2018)
 *lov_density_ave.g.mf_2 =metabolic density of grazers and 1/2 of mixed
 feeders (kg^b/kg^2); calculated using b=0.899 for wildlife (Lovegrove,
 2000) and 0.75 for livestock (Kleiber, 1932) ; After Staver et al. (2021)
 *order_density_ave.g.mf_2 = metabolic density of grazers and 1/2 of mixed
 feeders (kg^b/kg^2); calculated using b= order level average from (Genoud
 et al. 2018) *species_density_ave.g.mf_2 = metabolic density of grazers
 and 1/2 of mixed feeders (kg^b/kg^2); calculated using b= species level
 average when avaible from (Genoud et al. 2018)
 *weighted.ave.body.size.noele=average body size of grazer and mixed
 feeders weighted by metabolic density. Elephants are excluded.(kg)
 *proportion.nonruminant.noele=proportion of non-ruminant grazer and mixed
 feeders. Elephants are excluded. ### dataset_3:
 spatial.data.reserves.df.final.csv *mean_annual_BA= mean annual burned
 area (proportion) \* MAR = mean Annual rainfall (mm/yr) *sand = sand
 content (g/kg) *Seasonality = Average number of months 70% of annual
 precip falls in (number of months) *countries = country that this cell is
 in (country name) *reserve = reserve that this cell is in (reserve name)
 *tree_cover = tree cover (%) *Max_BA = maximum potential burned area
 calculated based on environmental variables (proportion) *Diff_BA =
 difference between Max_BA and mean_annual_BA (percentage points in
 proportion space) *Prop_BA =(difference between Max_BA and
 mean_annual_BA)/Max_BA (proportion) ###
 Fire_spatial_code_publication.final.R Code to analyze 1 km spatial and
 reserve scale burned area dataframe and to create figure 5. Figures were
 modified for aesthetics in adobe illustrator. ### Spatial_Data_retrival
 and processing_code_publication.final.R Retrieval and processing code for
 spatially explicit environmental variables from open data sources used to
 produce the products in this dataset (Burned area, rainfall, seasonality,
 tree cover, sand content) ## Sharing/Access information This is a section
 for linking to other ways to access the data, and for linking to sources
 the data is derived from, if any. Links to other publicly accessible
 locations of global products and shapefiles for the spatial datasets used:
 *[https://services5.arcgis.com/Mj0hjvkNtV7NRhA7/arcgis/rest/services/WDPA_v0/FeatureServer](https://services5.arcgis.com/Mj0hjvkNtV7NRhA7/arcgis/rest/services/WDPA_v0/FeatureServer) *[https://doi/org/10.17027/isric-soilgrids.713396fa-1687-11ea-a7c0-a0481ca9e724](https://doi/org/10.17027/isric-soilgrids.713396fa-1687-11ea-a7c0-a0481ca9e724) *[https://lpdaac.usgs.gov/products/gfcc30tcv003/](https://lpdaac.usgs.gov/products/gfcc30tcv003/) *[https://www.worldclim.org/data/bioclim.html](https://www.worldclim.org/data/bioclim.html) *[https://lpdaac.usgs.gov/products/mcd64a1v006/](https://lpdaac.usgs.gov/products/mcd64a1v006/) Link to KNP burned area and grass biomass data from Cardoso et al. (2022): *[https://datadryad.org/stash/dataset/doi:10.5061/dryad.ncjsxksxm](https://datadryad.org/stash/dataset/doi:10.5061/dryad.ncjsxksxm) Please see publication for methods and data publication citations ## Author Contributions ATK and ACS designed research. DMK, LMP and TPY provided data from the KLEE site at Mpala, Kenya. JRG, TRK, TMP and RMP provided data from the UHURU site at Mpala, Kenya. SEK, DEB, DIT, and MDS provided data from Kruger National Park, South Africa. ACS and WJB provided data from Hluhluwe iMfolozi Park, South Africa. TMA, NM and MER provided data from Serengeti, Tanzania. JAG and RMP provided data from Gorongosa National Park, Mozambique. GPH provided herbivore density data. ENF contributed to discussions regarding herbivore metabolic density comparison analysis. ATK analyzed data and primarily wrote the paper. All authors reviewed and edited the paper. ## Acknowledgments Funding for ATK and ACS was provided by three grants from the U.S. National Science Foundation (NSF; MSB-1802453 and DEB-2224317 to ACS, EAR-2204471 to ATK). U.S. National Science Foundation Funding for Kruger Exclosures was provided by NSF (DEB-0516145, DEB-0841917, DEB-0516094, DEB-1712786). The UHURU experiment was built and maintained with funding from the Sherwood Family Foundation, the National Sciences and Engineering Research Council of Canada (to JRG), the Universities of Florida and British Columbia, and the High Meadows Environmental Institute at Princeton University; research in UHURU has been supported by NSF (DEB-0709880, OISE-0852961, DEB-1355122, DEB-2225088 to RMP; DEB-0444071 to TMP; DEB-1930820 to TRK; DEB-1547679, NSF DEB-1930763, NSF DEB-2018405, and NSF-2132265 to JRG). Funding for KLEE exclosure plots at Mpala, Kenya provided by NSF (LTREB 97-07477, 03-16402, 08-16453,12-56034, and 19-31224 to TPY), the Smithsonian Institution, the National Geographic Society (4691-91 and 9106-12 to TPY), and the U.S. Fish and Wildlife Service (98210-0-G563 to TPY). The KLEE experiment was conducted under permit No. NCST/RCD/12B/012/42. Research in Gorongosa was supported by grants from NSF (IOS-1656527, DEB-2225088), the Cameron Schrier Foundation, the Carr Foundation, and the High Meadows Environmental Institute at Princeton University to RMP. TMA was supported by NSF (DEB-1145861 and BSC-1461728). ATK thanks members of the Staver Lab group for feedback on this manuscript. We thank David Augustine and Mahesh Sankaran for providing data from GLADE.