Reply to Ma and Zuo: Ecological restoration on the Tibetan Plateau would benefit terrestrial CO2 uptake.

We welcome a new comment on our paper and appreciate the opportunity to clarify our thinking (1). We are happy that they agree with the notion of a strengthening CO2 sink of the Tibetan Plateau (TP) (2). We agree with the importance of the influence of human activities on the CO2 sink (1), and here we clarify that incorporating this aspect into consideration would also support our viewpoint.

Grazing Activities Captured by Eddy Covariance (EC)

The height of the EC sensors ranges from 1.94 to 4.5 m (2), i.e., a footprint with a diameter of ∼200 to ∼500 m, which is much larger than the fences of 10 to 50 m (to avoid damage to the EC equipment caused by animals). We verified that 30 out of the 32 sites are affected by livestock grazing (Haibei #6 and Shule River remained unknown). This means that the EC sensors already captured the contribution of grazing, which enabled us to provide a reasonable evaluation of the CO2 sink (2).

Decreased Grazing Density under Ecological Restoration and Protection

During the past several decades, part of the vast alpine pastures has experienced overstocking-induced degradation, which has also been witnessed in the Zoige wetlands (1). To tackle this, the Retire Livestock & Restore Pastures program was initiated in the 2000s (3–5), in which 176 out of 213 counties in severely degraded areas were fenced for restoration and livestock numbers decreased by 20%. Ecological restoration/protection is widely reported as promoting a net CO2 sink, by 16 to 47% (6–8). The ongoing restoration/protection measures implemented across the TP, such as the Three-River-Source National Park, Qilian Mountains National Park, and Tibetan Plateau National Park Cluster, would benefit the CO2 sink by further reducing the grazing density.

Increase of Alpine Wetland Extent on the TP since the 2000s

The Zoige wetlands were subjected to drainage before the 2000s followed by restoration thereafter—specifically, 200+ km of ditches refilled for restoration (9). This drainage–recovery story is limited to Zoige, which accounts for 5% of the wetlands area of the TP. Furthermore, the Zoige wetlands are permanently inundated (so drainage is needed for grazing), though 89% of alpine wetlands on the TP are seasonally inundated (10), where there is no need to apply drainage for grazing. In fact, the alpine wetland extent has experienced a precipitation-driven increase since the 2000s (11), rather than a drainage-induced decline.

Therefore, we clarify that the EC sensors captured the grazing activity to guarantee a reasonable evaluation of the CO2 sink. The ongoing changes in human activities, i.e., large-scale restoration and protection of these fragile ecosystems (Fig. 1), witnessed by us during the past 20 y, are expected to benefit regional CO2 sinks under the warming and wetting climate.

Fig. 1.

Various ecological restoration and protection projects across the TP.