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Addressing intertwined crises of climate change and biodiversity loss is a pressing global challenge, with trees playing pivotal roles in promoting carbon sequestration and habitat diversity. However, there is a distinct knowledge gap concerning the global drivers shaping tree cover and its heterogeneity, particularly the roles and relative importance of large herbivores and fire compared to climatic and topo-edaphic conditions. Here, we deploy satellite observations of strictly protected areas worldwide to reveal that in regions where vegetation may be in disequilibrium with climate, high biomass of large herbivores, especially browsers, is inversely related to tree cover but positively associated with its spatial heterogeneity. Conversely, fire reduces both tree cover and heterogeneity. These results suggest that top-down megafauna effects on landscape-scale vegetation openness and heterogeneity manifest worldwide. Our finding supports the need to consider megafauna, particularly large herbivores, in ecosystem effects on climate change mitigation and conservation and restoration efforts through trophic rewilding.

•The Iberá rangeland showed overall net greening but also substantial local browning.•Rangeland greening is linked to land use, surface water changes, fire, and climate.•Fire tended to reduce the greening both in protected and unprotected areas.•Woody expansion driven by tree plantations occurred mainly in unprotected land.•Overall greening resulted from multiple trends has a negative impact on biodiversity.

Changes in the phenology of vegetation activity may accelerate or dampen rates of climate change by altering energy exchanges between the land surface and the atmosphere and can threaten species with synchronized life cycles. Current knowledge of long-term changes in vegetation activity is regional, or restricted to highly integrated measures of change such as net primary productivity, which mask details that are relevant for Earth system dynamics. Such details can be revealed by measuring changes in the phenology of vegetation activity. Here we undertake a comprehensive global assessment of changes in vegetation phenology. We show that the phenology of vegetation activity changed severely (by more than 2 standard deviations in one or more dimensions of phenological change) on 54% of the global land surface between 1981 and 2012. Our analysis confirms previously detected changes in the boreal and northern temperate regions. The adverse consequences of these northern phenological shifts for land-surface–climate feedbacks, ecosystems and species are well known. Our study reveals equally severe phenological changes in the southern hemisphere, where consequences for the energy budget and the likelihood of phenological mismatches are unknown. Our analysis provides a sensitive and direct measurement of ecosystem functioning, making it useful both for monitoring change and for testing the reliability of early warning signals of change.

The article discusses the nonprofit organization BirdLife South Africa's development of the Golwe Vhurivhuri and Gundani Mutsiwa campsites in Venda, South Africa. Funding for the project was received from the Swiss South African Cooperative Initiative (SSACI). In addition to refurbishments, the campsites also have been equipped with luxury safari tents, hot showers and flushing toilets. Rare birds that ornithologists and bird watchers can see at each campsite are also described.