In this Special Issue of Science, a Perspective and four Reviews highlight the unrecognized value of grasses – a highly diverse collection of plant species that supply crucial ecosystem services and resources. Not only do they provide a major source of food for humans, grassland ecosystems also constitute nearly 40% of the terrestrial biosphere, harboring a great diversity of animals and plants. But grasslands are threatened by continued land-use conversion and climate change. "Grasses could offer solutions to many of our current societal challenges if only we fully recognize their diversity and value," write Science Associate Editor Bianca Lopez and colleagues in the issue's introduction.
These points are echoed in a Perspective by Caroline Strömberg and A. Carla Staver. According to the authors, the history of humans as a species has been closely tied to grassy biomes for millions of years. Our earliest ancestors evolved in savannas and agricultural societies arose alongside the domestication of grasses like wheat and barley, which provided a critical source of food for growing populations as they continue to do today. However, grassy biomes are predicted to be some of the hardest hit ecosystems by ongoing climate change and other human impacts. Here, Strömberg and Staver argue that as the importance of these critical regions becomes more recognized, there is a need to better understand their past and present functions to inform policy and management.
Global grasslands have undergone significant destruction and degradation due to climate change and human activity. In a Review, Elise Buisson and colleagues discuss grassland restoration and the recent research that suggests that grassland recovery occurs slowly or not at all; what's more, interventions to speed up or guide efficient recovery are not well understood, particularly when compared to what is known about forest ecosystem recovery. According to Buisson et al., it has been assumed that grasslands are relatively recently formed biomes and are quick to rebound following disturbance. The authors argue that grassland restoration needs to be viewed as a long-term process toward old-growth endpoints. "As we enter the United Nations Decade on Ecosystem Restoration, advances in restoration science and practice in grasslands are critical if we are to combat the loss of old-growth grasslands and the decline of biodiversity," Buisson et al. write.
A Review by Yongfei Bai and M. Francesca Cotrufo highlights research that shows how preserving grasslands and increasing their plant diversity can boost soil organic carbon storage. Grasslands store roughly one-third of global terrestrial carbon stocks and can continue to act as an important soil carbon sink. According to the authors, improved grassland management can provide low-cost and/or high carbon gain options for natural climate mitigation solutions.
Paula McSteen and Elizabeth Kellogg, in their Review, highlight the genetic and evolutionary processes that have led to the large diversity of grasses we see worldwide today, encompassing nearly 12,000 species, including several that directly and indirectly feed much of humanity.
Lastly, a Review by Richard Unsworth and colleagues focuses on seagrasses – a unique group of underwater flowering plants. Like terrestrial grasses, seagrasses form meadows in shallow seas worldwide, providing important resources for fisheries, coastal protection and climate mitigation. However, these biomes, too, are at risk. Unsworth et al. provide an overview of the past and present distribution of seagrasses and the ecological role they play. Moreover, the authors offer suggestions on seagrass habitat conservation to ensure their persistence.
