However, the impact of elevated temperatures on the land sink is more than a function of cumulative area. Biomes that cycle 40 to 70% of all terrestrial carbon (19) including the rainforests of the Amazon and Southeast Asia and the Taiga forests of Russia and Canada are some of the first to exceed biome-specific for half the year or more. This reduction in land sink strength is effectively front-loaded in that a 45% loss occurs by midcentury, with only an additional 5% loss by the end of the century (Fig. 3D). Furthermore, these estimates are conservative as they assume full recovery of vegetation after temperature stress and ignore patterns and lags in recovery (25).
Basically, as net positive climate forcings increase, we will continue to decrease net carbon capture by the terrestrial ecosystems of the earth as a whole. (LS)
The temperature tipping point of the terrestrial biosphere lies not at the end of the century or beyond, but within the next 20 to 30 years (Figs. 2 and 3, A to D). Given the temperature limits of land carbon uptake presented here, without mitigating warming, we will cross the temperature threshold of the most productive biomes by midcentury, after which the land sink will degrade to only ~50% of current capacity if adaptation does not occur. While biomes will eventually shift spatially in response to warming, this process is unlikely to be a smooth migration, but rather a rapid disturbance-driven loss of present biomes (with additional emissions of carbon to the atmosphere), followed by a slower establishment of biomes more suited to the emerging climate. Furthermore, the establishment of new biomes is unlikely to be complete without human intervention and will be limited by edaphic factors, especially nutrient availability. This further suggests that we are rapidly entering temperature regimes where biosphere productivity will precipitously decline and calls into question the future viability of the land sink, along with Intended Nationally Determined Contributions (INDCs) within the Paris Climate Accord, as these rely heavily on land uptake of carbon to meet pledges (33)