Bastin et al.’s estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of savannas, grasslands, and shrublands to be restoration.

Earth’s ancient grasslands and savannas—hereafter old-growth grasslands—have long been viewed by scientists and environmental policymakers as early successional plant communities of low conservation value. Challenging this view, emerging research suggests that old-growth grasslands support substantial biodiversity and are slow to recover if destroyed by human land uses (e.g., tillage agriculture, plantation forestry). But despite growing interest in grassland conservation, there has been no global test of whether old-growth grasslands support greater plant species diversity than secondary grasslands (i.e., herbaceous communities that assemble after destruction of old-growth grasslands). Our synthesis of 31 studies, including 92 timepoints on six continents, found that secondary grasslands supported 37% fewer plant species than old-growth grasslands (log response ratio = −0.46) and that secondary grasslands typically require at least a century, and more often millennia (projected mean 1,400 y), to recover their former richness. Young (<29 y) secondary grasslands were composed of weedy species, and even as their richness increased over decades to centuries, secondary grasslands were still missing characteristic old-growth grassland species (e.g., long-lived perennials). In light of these results, the view that all grasslands are weedy communities, trapped by fire and large herbivores in a state of arrested succession, is untenable. Moving forward, we suggest that ecologists should explicitly consider grassland assembly time and endogenous disturbance regimes in studies of plant community structure and function. We encourage environmental policymakers to prioritize old-growth grassland conservation and work to elevate the status of old-growth grasslands, alongside old-growth forests, in the public consciousness.

Biodiversity of tropical grasslands and savannas (tropical grassy biomes, TGBs) remains poorly documented compared with tropical forests.

The fact that plant spatial aggregation patterns shape insect-herbivore communities in a variety of ways has resulted in a large body of literature on the subject. The landmark resource concentration hypothesis predicts that density of insect herbivores per plant will increase as host plant density increases. I examined this prediction across temporal samplings using Jatropha nana and the associated specialist insect herbivores as a system. Through 12 field samplings, I modelled the effect of host plant density on insect-herbivore loads. The initial samplings (2–3) provided evidence for the resource concentration hypothesis, with insect loads increasing with increasing host plant density, whereas the later samplings (4–5, 7–11) showed the opposite; a resource dilution pattern with a decline of insect loads with increasing host plant density. These patterns also depend on the biology of the herbivores and have important implications on J. nana population dynamics..

Woody plant encroachment is a pervasive global driver impacting grassland structure and functioning, and we know very little about efficacies of management techniques for restoring woody plant-encroached tropical grasslands. In the Banni grasslands of India, which are extensively encroached by an invasive woody legume, Prosopis juliflora, we test the efficacies of two Prosopis management methods-mechanical removal and lopping-to restore native grasslands. Across eight sites in the Banni, using a randomized block design, we monitored herbaceous plant recovery in the two Prosopis management treatments, and an unmanipulated control for 4 years. We also sampled four reference grasslands. We found native herbaceous plant richness and cover to be threefold (mean = 6 species) and sixfold (mean = 18% cover) higher, respectively, in the mechanical-removal treatment compared to the control (mean richness = 2 species, cover = 3%), but found no significant differences between the lopping treatment (mean richness = 5 species, cover = 11%) and the control. While mechanical-removal increased plant diversity, neither management treatment changed the species composition, and both of these treatments were still missing perennial grasses that dominate the reference grasslands. Our data highlight the efficacy of mechanical removal over lopping in restoring native grasslands. However, mechanically removing Prosopis is costly, especially at larger scales. Apart from its detrimental impact on grasslands, Prosopis also has benefits varying with stakeholder groups, and its removal involves complex trade-offs. Until we fully understand the trade-offs involved, it may therefore be better to manage this social-ecological landscape as a mosaic of restored grassland and Prosopis-invaded patches.

We monitored native forest regeneration over 11 y in a eucalyptus plantation and compared it with the neighbouring primary forest. For the plantation forest, we hypothesized that species richness, density, basal area and densities of old-growth species would increase over time, and compared to the primary forest, plantation forest would have higher species richness and density, but lower densities of old-growth species. In 2016, we repeated the protocol of a study that sampled the plantation forest in 2005, with thirty 10 × 10-m plots and enumerating trees (≥10 cm diameter), saplings (>1 to <10 cm diameter) and seedlings (<1 cm diameter). In the plantation forest, for trees, the species richness, density of gap, bird-dispersed and mammal-dispersed species increased by 67%, 156%, 116% and 238% respectively; whereas for saplings, density of gap, bird-dispersed and small-seeded species declined by 45.2%, 51% and 18.2% respectively over time; and seedling densities did not change across functional groups. Stand basal area increased by 80.1% in the plantation forest. The primary forest had 446% greater density of closed-canopy trees compared with plantation forest. Contrary to our prediction, the plantation forest did not accumulate significant densities of old-growth species over time, probably due to demographic filters that prevent them from attaining maturity.

In the present communication, we resurrect E. khandallensis and synonymize E. panchganiensis under it owing to the overlap of distinguishing characters, as inferred from literature and first hand observations. We further provide an amended description of E. khandallensis along with critical notes on its taxonomy and distribution.

Trissolcus jatrophae Rajmohana et al. 2011, a parasitoid wasp has been observed to parasitize hemipteran eggs laid on Jatropha nana Dalzell & Gibson (Euphorbiaceae) growing in Pune city, Maharashtra. In the present communication, this wasp has been reported for the first time on a new host plant species, and the occurrence of this wasp also forms a new distributional record.