This paper aims to reveal the responses of global natural vegetation to future climate change in the twenty-first century. Thus, the dynamics of terrestrial net primary productivity (NPP) in three time slices, namely, 2030s, 2050s and 2070s are projected using a segmentation model that utilized 25 global climate models under the Representative Concentration Pathway 2.6 (RCP2.6) scenario. The results showed that forests would expand at the expense of grasslands and deserts in the current century. Terrestrial NPP is projected to increase globally from 127.04 ± 1.74 Pg DW·a−1 in 2030s to 127.62 ± 2.57 Pg DW·a−1 in 2070s. Temperate forest, the largest distributed vegetation, would contribute the most to the overall increase (548.50 Tg DW·a−1). The NPP of warm desert, savanna, and tropical forest is projected to increase by 31.03, 248.45 and 111.25 Tg DW·a−1, respectively. By contrast, the NPP of all the other vegetations would decline at the end of this century. In the tropical and the south temperate zones, terrestrial NPP is projected to decrease by 99.32 and 25.56 Tg DW·a−1, respectively, with the difference lying in the increasing–decreasing trend in the former and the continually decreasing trend in the latter. However, terrestrial NPP in the north temperate and north frigid zones is projected to increase consistently by 639.43 and 57.73 Tg DW·a−1, respectively. The “increase-peak-decline” trend of greenhouses gases described in the RCP2.6 would lead to the warming and cooling periods during this century. The vegetation NPP of various ecosystems or climate zones would respond differently to the future climate change. In general, ecosystems in northern high latitudes would become more vulnerable to future climate change compared to other vegetations.