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The livestock sector is a key driver of humanity's transgression of several planetary boundaries, with the production of ruminant meat being particularly impactful. Given current trends in demand for animal products, strategies to significantly reduce the livestock sector's environmental impacts are urgently needed. Here we draw on published data to examine livestock's impacts in three key critical sustainability domains within the planetary boundaries framework climate change, biochemical flows and land-system change, and seek to quantify livestock's occupation of humanity's safe operating space now and into the future (2050). We estimate that the livestock sector may already occupy the majority of, or transgress, humanity's safe operating space across these domains, with such impacts forecast to grow by 2050. Furthermore, we explore the potential of reasonably foreseeable technological measures to mitigate the sector's environmental impacts. While such measures are deemed necessary, their effects are unlikely to be sufficient to shrink the scale of livestock's impacts to a sustainable level, as defined by the three planetary boundaries tested. The implication of these findings is that macroeconomic policies promoting both sustainable production and consumption practices are integral to the realisation of a sustainable food system, where humanity functions within its safe operating space.