Comment on Wilson and Edwards' proposal for low‐emission meat

Abstract

George Wilson and Melanie Edwards are to be commended for raising the issue of livestock methane in their recent paper “Native wildlife on rangelands to minimize methane and produce lower-emission meat: kangaroos versus livestock” (Edwards & Wilson 2008). However, the paper contains inconsistencies and the proposed massive increase in kangaroo meat production is implausible. First the inconsistencies. Table 2 claims that 34 million kangaroos with a kill rate of 15% will produce 170,000 tonnes of carcase. That is about 33 kg per animal. But the table implies a carcase weight of 12 kg which is consistent with other studies (Hardman 1996; Hacker et al. 2004). The 33 kg carcase weight is also evident throughout figure 3. The overestimate of carcase weight yields an almost three-fold underestimate of the animals required to produce the desired amount of carcase. We all make numerical mistakes, but a more serious issue is that a beef carcase is different from a kangaroo carcase. A beef carcase can yield 60% to 70% of its carcase weight as cuts or mince (Yeates & Gaden 1998). The Kangaroo Industry Strategic plan 2005–2010 (Kelly 2005) uses a figure of just 1.5 kg (12%) per kangaroo as cuts with the rest of the carcase being only suitable for processed meat. Thus, it will take 120 kangaroo carcases with a combined weight of 1.4 tonnes to provide the same quantity of meat cuts as a single 260 kg cattle carcase. This brings the accumulated underestimate of the kangaroo population required to over 15-fold. The authors claim that reductions in sheep numbers will allow a kangaroo population increase but present a graph (figure 1) showing that the 2006 kangaroo population has had a net decline of 15 million since 1990 despite a reduction in the sheep population 170 million to 88 million during the same period (Pink 2008). In summary, Wilson and Edwards seriously underestimate the kangaroo population required to replace the suggested reduction in sheep and cattle and fail to identify an adequate mechanism to drive kangaroo population growth. Editor : Corey Bradshaw