apparently, switching from cows + sheep to kangaroo as a source of red meat could reduce Australia's total carbon output by 3%, mainly because kangaroos produce less methane.
the study also mentions a few other small issues, such as reduced erosion from padded feet versus hooves. glaringly absent is a look at Australia's most constrained resource: water. drought is the normal state of affairs in Australia recently and i've mentioned before how much more effective their water restriction policies could be if they included dietary considerations.
presumably, kangaroo production is less water intensive than beef production, since kangaroos are more natural animals raised in more natural ways and native to the region. if so, then it'd be a comparatively simple matter of setting policy to encourage kangaroo consumption as a nationalistic and environmentally friendly alternative. to drive the point home, it may even be worthwhile to look at including an "excess water use and erosion" tax on beef.
for reference, kangaroo meat is already sold in normal grocery stores in Australia, so for the generality of the population to switch to this alternative would not be as odd as it would be for Americans to switch to deer, which is rarely found in grocery stores here. psychologically, i think it'd be more like Americans switching from beef to sheep.