What is a grassland?
What is a grassland and what are its key features?
A grassland is an area where vegetation is predominantly composed of grasses (Poaceae). It can also include sedges, rushes, legumes like clover, and other herbaceous plants. Grasslands are generally open, continuous, and relatively flat areas without significant woody shrubs. The height of the grass can vary, often related to rainfall, and they are typically maintained as a stable state by factors such as fire, grazing, drought, freezing temperatures, or human management like mowing.
Grasslands can be classified in various ways. One common classification is by their origin and management, differentiating between natural and human-influenced types. Semi-natural grasslands, a result of human activities like grazing or mowing, are prevalent in places like northwest Europe. These are further categorised based on agricultural modification: "unimproved" (high biodiversity, no modern pesticides/fertilisers), "semi-improved" (some modification, some conservation value), and "agriculturally improved" (heavily modified, low diversity). Another classification is based on soil pH: acid (pH < 5.5, generally species-poor), neutral (pH 5.5-7.0, diverse communities), and calcareous (pH > 7.0, often very species-rich, particularly ancient chalk grasslands).
Semi-natural grasslands are those that have developed due to human activities like grazing or mowing, where natural processes still maintain the environmental conditions and species pool. They are often highly biodiverse, especially if they are "unimproved" and haven't been treated with modern agricultural chemicals. Agriculturally improved grasslands, in contrast, are heavily modified by practices such as ploughing, reseeding, heavy fertilisation, or intensive grazing. This 'improvement' typically leads to a significant reduction in wild plant diversity, resulting in a limited range of common species.
Grasslands are vitally important for several reasons. They are highly biodiverse, serving as crucial habitats for a vast array of species including wildflowers, fungi (like waxcaps), invertebrates, reptiles, amphibians, small mammals, bats, and birds. They support a significant proportion of priority species for conservation. Wildflower-rich grasslands are essential for pollinators, including bees and butterflies, many of which have suffered catastrophic declines due to the loss of meadow habitat. Grasslands also hold historical and cultural value, having often developed over centuries through human interaction like grazing and mowing, creating valued cultural landscapes.
Despite covering large areas, biodiverse grasslands, particularly unimproved ones, are under severe threat. Semi-natural grasslands are globally scarce, with significant losses in Europe during the 20th century. The UK has experienced a dramatic decline, losing an estimated 97% of its species-rich grassland since the 1930s, primarily due to ploughing for crops. The decline of semi-natural lowland grassland has been particularly severe, making unimproved grassland one of the most threatened habitats with many species depending on it.
Management is crucial for maintaining the diversity and abundance of plant species in grasslands. Without intervention, grasslands are dynamic habitats that would naturally progress through ecological succession to scrub and eventually woodland within around 50 years. Management practices like grazing or mowing prevent competitive species and scrub from dominating, effectively holding the grassland in a stable state. This is why grasslands are often considered plagioclimax communities, maintained by ongoing disturbance or management.
Different types of grassland management include pasture and meadow. Pasture refers to grassland that is grazed by livestock. Meadow is grassland that is harvested for hay or silage, although it may also be grazed after cutting. Traditional hay meadows, typically cut once a year with the hay removed, are known for their rich floral diversity. These management practices prevent the natural succession of the habitat towards scrub and woodland.
UK grasslands are largely described as semi-natural because they have often developed and been maintained over centuries through human activities like grazing and mowing, particularly after Neolithic people cleared forests. When these grasslands are species-rich and haven't been heavily modified by modern agricultural practices, they are often referred to as unimproved. They are considered threatened due to the dramatic loss of species-rich grassland, estimated at 97% since the 1930s, primarily due to land use changes like ploughing for crops. This decline underscores their urgent need for preservation.