What do changing rainfall patterns mean for the world's nourishing grasslands?

Irish Times

22-05-2025

Grasslands are more than grass. Meadows (mown) and pastures (grazed) supporting orchids, daisies and the edgily named devil's-bit scabious are looking at their best right now.
Less intensively managed or semi-natural grasslands include Ireland's most diverse ecosystem in the Burren and support populations of many species of rare and beautiful insects and birds. Visiting a gorgeous bit of grassland near you has never been easier with the launch of
The Grasslands Trail
, including 27 public and private sites, many of which are publicly accessible.
More than 40 per cent of the world's terrestrial surface, and 60 per cent of Ireland, is covered by grasslands. But the word 'grassland' doesn't do justice to the massive diversity of different kinds of grass-dominated ecosystems. Grasslands range from the sparse and spiky deserts of Australia's red centre, supporting huge flocks of budgerigars, to the lush green rain-fed grasslands of Ireland.
A
recent study
of grassland responses to rainfall published in the Proceedings of the National Academy of Sciences shows the global importance of what every farmer in Ireland going through this spell of dry weather knows, rain is critical to grassland productivity.
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The study also shows the response of grassland productivity to rainfall changes depending on whether the critical nutrients of nitrogen and phosphorus are added. Adding both nitrogen and phosphorus to a grassland boosts productivity across the whole rainfall gradient from deserts to the soggy west coast of Ireland.
In a wet climate such as ours, adding critical nutrients means the grasses that rapidly use those nutrients, together with the available water, can grow quickly and dominate. This explains the different kinds of grasslands we find here.
Burren flowers. Photograph: Burren Ecotourism Network
Irish grasslands range from the fertiliser-dependent monocultures of a single-pasture grass species, perennial rye grass, to the massively diverse Burren grasslands, which support more than 1,000 plant species, three-quarters of all the plant species in Ireland. This grassland diversity gradient is governed by how naturally fertile the soil is and the type and quantity of nutrients added through chemical or organic fertilisers.
The
higher the nutrients
in the soil, the fewer species of plants are found in a grassland. This has knock-on effects for the animals that use grasslands for food and nesting. The recent launch of the
butterfly atlas of Ireland
shows there are ongoing precipitous declines in the abundances and distributions of our most common butterfly species.
Many butterfly species are dependent on a
diversity of grassland plants
to support the needs of caterpillars for the right kinds of leaves and adult butterflies for nectar from flowers.
Grasslands have supported human civilisation for millenniums. Breakfast porridge, our daily bread and the rice that sustains more than half of the world's population are all bred from grasses that naturally occurred in the wild.
Wild relatives of these cultivated grasses are still a critical resource for providing additional genetic material that is used to breed new cultivars, adapted to our changing climate and soils. Grasslands underpin
Ireland's livestock industry
and the production of meat and milk.
Permanent, unploughed grasslands provide
carbon removal services
by locking carbon from the atmosphere away in soils, and the grasslands of the Shannon Callows provide space for overflowing rivers to spread, saving downstream towns and cities from flooding. Flower-rich grasslands like the dunes in Derrynane or the winter-grazed pastures of the Burren support important tourism industries and, if managed sustainably, can jointly benefit local economies and biodiversity.
A changing climate will disrupt the pattern of rainfall across the country, changing when and how the grass grows. Reducing the emission of fossil fuels and methane from livestock into the atmosphere will reduce the impacts of climate change worldwide and here in Ireland.
However, a better understanding of how rainfall and nutrients together affect grass production will be critical to adapting to new conditions for farming and conservation over the next decades.
The global study of grasslands, which included the Burren was funded by the US National Science Foundation, an agency that is facing extreme cuts in funding for work on biodiversity and climate. Ireland and Europe will need to step up research efforts to fill this gap in understanding how grasslands can be managed under an uncertain future climate.
Yvonne Buckley is professor of zoology at Trinity College Dublin and co-director of the
Climate + Co-Centre for Climate, Biodiversity and Water
and director of AIB Trinity Climate Hub