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A global assessment of Holistic Planned Grazing™ compared with season-long, continuous grazing: meta-analysis findings
Hawkins, Heidi-Jayne. 2017. "A global assessment of Holistic Planned Grazing™ compared with season-long, continuous grazing: meta-analysis findings."  African Journal of Range & Forage Science 34 (2):65-75.

Key Takeaways

  • This paper performs a “quantitative meta-analysis” of 21 grazing studies that are claimed to represent Holistic Planned Grazing (HPG) in a comparison with performance data from year-long continuous grazing.
  • The paper finds no significant difference in plant basal cover, plant biomass and animal performance and thus refutes claims that HPG is superior in those areas. It does not say it is inferior, only that there is no meaningful difference.
  • The rigor of this paper is itself refuted by Frith (2017) which argues that Hawkins misattributed her reviewed studies to HPG, when, in fact, they were not representative of it. Upon closer investigation, Frith finds that those papers that were most closely aligned with the HPG protocol - including elements such as adaptive stocking densities and rest periods - actually showed the best performance along the measured categories, and, thus, provided evidence favorable to HPG, not the opposite, as Hawkin’s claims.

Read the rebuttal to this paper: “Hawkins’s 2017 Meta Analysis of Holistic Planned Grazing Should be Retracted

Summary

It has been claimed that Holistic Planned Grazing™ (HPG), a type of rotational grazing, can increase productivity in rangelands and reverse climate change while doubling the stocking rate, mainly through the impact of densely bunched animals on primary production. Previous reviews have found similar or greater plant and animal production in continuous (season-long) compared with rotational grazing. Here season-long continuous grazing is compared with HPG alone to explore the evidence for animal impact. Three quantitative meta-analysis models were used to assess data sets from literature between 1972 and 2016. Weighted mean differences (effect sizes) between HPG and continuous grazing showed that there was no difference in plant basal cover, plant biomass and animal gain responses (p > 0.05). Thus, from the balance of studies, if animal impact is occurring during HPG, it has no effect on production. As interesting as the overall result is the significant between-study heterogeneity assessed using Cochran’s Q (p = 0.007 to <0.0001). Studies with positive effect sizes tended to have higher precipitation (p < 0.05), suggesting that only some rangelands have the resources to support HPG. Furthermore, there is scope for investigating the impact of HPG on socio-ecological aspects of rangelands, such as management.

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