Grazing and trampling exert important influences on vegetation structure (Clarke 1948). Heavy grazing by cattle and sheep on fertile soils can produce a short, dense sward of neutral grassland species such as Lolium perenne, which is unsuitable for grasshoppers (Gardiner et al. 2002). However, Clarke (1948) suggested that excessive grazing by rabbits on chalk grassland and heaths promoted sparser vegetation, comprised of less vigorous species such as Festuca ovina, which was consequently more favorable to grasshoppers.

In another study on a heavily rabbit-grazed calcareous grassland, C. brunneus was more abundant within an exclosure than on the surrounding grazed grassland (Grayson and Hassall 1985). The authors suggested that the taller vegetation in the exclosure provided better cover from vertebrate predators and better quality food resources for grasshopper nymphs than the shorter grazed vegetation. In coastal pastures which have been ungrazed for many decades on Skipper’s Island in southern England, the species richness of orthopteroids is higher than in mainland habitats such as sea wall flood defenses where mowing management is undertaken (Gardiner and Ringwood 2010). These ungrazed pastures have developed a mosaic of tussocky, rank grassland and scrub which is suitable for grasshoppers and bush crickets.

A large mesa in South Africa acted as a refuge for Orthoptera in comparison to the heavily grazed flatlands which surrounded it (Gebeyehu and Samways 2006). The summit, which was inaccessible to grazing livestock, was an important conservation refuge for one grasshopper species, Orthochtha dasycnemis.

Across Europe, overgrazing (particularly by cattle) is the greatest threat to Orthoptera (affecting 262 species; Hochkirch et al. 2016). In the UK, concerns have been raised about the negative effect of pony overgrazing upon the orthopteran assemblages of the New Forest (Tubbs 1986, Pinchen 2000, Denton 2006). Denton (2006) outlines the importance of exclosures, from which grazing ponies are largely excluded, for Orthoptera in the forest. For example, both the nationally scarce Omocestus rufipes and Nemobius sylvestris are found in exclosures, the varied and taller vegetation structure created in the absence of excessive grazing being particularly important. Surveys along the Mardyke River Valley in the UK also showed that Orthoptera were extremely scarce in intensively grazed horse pastures and that species richness was lower than in ungrazed grassland (Gardiner and Haines 2008). The horses grazed continuously throughout the year on the south side of the Mardyke and this led to an extremely short sward (<100 mm in height) that may have provided insufficient cover from inclement weather and predators (particularly birds) for Orthoptera (Gardiner et al. 2002).

A study of rangeland grasshoppers in the USA found that most grasshopper species were more abundant on ungrazed treatments when compared to heavily grazed areas (O’Neill et al. 2003). However, one species, Aulocara elliotti, a serious pest of rangelands, preferred the heavily grazed plots, perhaps due to its exclusion from densely vegetated pasture. Conflicting evidence is provided in Holmes et al. (1979) who stated that some grasshopper species were more abundant in heavily grazed fields when compared with lightly grazed fields, while other species exhibited the opposite preference for infrequently grazed pastures with tall and dense vegetation. Cease et al. (2012) also demonstrated that abundance of the locust Oedaleus asiaticus was promoted by heavy grazing in north Asian steppe grasslands by the lowering of plant nitrogen (N).

In savannah grassland in South Africa, abundance and guild structure of grasshoppers varied between lightly and heavily grazed areas (Prendini et al. 1996). The heavily grazed areas characterized by short vegetation were dominated by grasshopper species associated with short grass and/or bare earth, whereas the lightly grazed grassland with taller and thicker grass had mainly grasshoppers of taller vegetation which were mixed feeders or tough grass feeders (Prendini et al. 1996).

Fire and grazing are two of the main methods of grassland management, and in many areas they interact to influence populations or assemblages of Orthoptera. In Afromontane grasslands in South Africa, grasshopper abundance benefited greatly from burning and cattle grazing (Joubert et al. 2016). Most grasshoppers favored recently grazed or burned grassland, although some did not, further highlighting the species-specific response to grazing management observed in other studies.

In the UK, traditional Culm grassland management, such as grazing and burning, has been undertaken to restore neglected sites (Wolton 1991). Grazing of pastures usually occurs between late May and late September, at a stocking rate of approximately 1 suckler cow per ha over a period of 20 weeks, leading to a diverse sward about 150 mm in height (Wolton 1991). Winter burning (known as swaling) during January or February is also practiced and has traditionally been used after particularly wet summers when it is impossible to graze livestock. This burning reduces the quantity of leaf litter, therefore providing a more open sward (Ausden and Treweek 1995). The complex interaction between weather and grassland management has important effects on Orthoptera populations.

In a small-scale study of formerly grazed Culm grasslands subjected to burning, there was increased Orthoptera abundance (density 29X greater on burned plots than on unburned replicates) in the post-burn year (Gardiner et al. 2005), as in the studies of Samways (1994) and Bieringer (2002). It is likely that mesophilous species such as C. parallelus, which overwinter as egg pods in the soil, may escape the main destructive impact of winter burning. The reduced sward height/biomass and increased light penetration on winter-burned swards in April/May could lead to enhanced post-diapause development and basking opportunities for hatched nymphs. Recently-burned ground could also be attractive to melanic groundhoppers (Tetrix undulata; Gardiner 2012) and grasshoppers (Myrmeleotettix maculatus; Gardiner 2014). Grazing in the post-burn year could keep the vegetation open and prevent development of a tall, tussocky Molinia caerulea sward.

Hochkirch et al. (2016) suggest that wildfires are a significant threat to 173 European Orthoptera species, with bush crickets (Tettigoniidae) more threatened than grasshoppers (Acrididae), perhaps due to many bush cricket species being flightless and unable to escape from the flames.

As most grassland exists at a relatively early stage of succession, abandonment of grazing can be particularly harmful to the Orthoptera assemblages reliant on the open sward, with 148 European species affected (Hochkirch et al. 2016). In Epping Forest in the UK, the locally-scarce grasshopper O. viridulus was significantly more abundant on cattle-grazed sites than in ungrazed grassland and heathland (Gardiner 2010). The absence of grazing in particular, led to scrub encroachment and natural woodland succession throughout the open plains in the forest, causing major declines in floristic and thermophilous insect diversity in the 20^th century (Rackham 1986). Despite these losses, Epping Forest is still considered one of the most important areas for Orthoptera in Essex County (Wake 1997), with new species such as Stenobothrus lineatus colonizing the open plains (Wilde 2009), perhaps in response to climate change (Gardiner 2009).

Rare species in the UK, such as D. verrucivorus, which are on the edge of their range, have very specific micro-habitat requirements (Cherrill and Brown 1990, 1992). D. verrucivorus was formerly found on several heathland sites in southern England, but with the loss of these populations, it is now restricted to ancient calcareous grassland (Fig. 3). D. verrucivorus disappears very quickly if winter-cattle-grazing ceases and tall rank grasses such as Brachypodium pinnatum encroach onto the bare ground. These rank grasses replace the low, herb-rich turf that D. verrucivorus requires for oviposition and which its early nymphal stages require for quick development in the warm microclimate provided by the open niches of this turf (Sutton 2015).

Fig. 3. 

Grazed chalk downland in Sussex, UK, habitat for the rare Decticus verrucivorus, credit T. Gardiner.

Conversely, abandonment of cattle livestock grazing in Spanish grasslands had an immediate positive effect on density, diversity and species richness of Orthoptera, although the effects were species-specific (Isern-Vallverdu and Pedrocchi 1994). The ungrazed pastures had taller grasses which were generally more favorable for Orthoptera because they had more refuges than the formerly grazed habitats. Species which benefitted from abandonment of grazing in Isern-Vallerdu and Pedrocchi’s (1994) study included S. lineatus and large species such as Platycleis tessellata which needed the cover from avian predation. One species which was associated with short grassland and bare ground, M. maculatus, disappeared with the abandonment of cattle grazing. This may explain its extirpation from Epping Forest in the UK where cattle grazing ceased in the 20^th century, although cattle grazing was reintroduced in 2002 and has since been linked to an increase in abundance of O. viridulus (Gardiner 2010; Fig. 4).

Fig. 4. 

Cattle grazed wet grassland in Epping Forest, UK, habitat for Omocestus viridulus, credit T. Gardiner.

The type of grazing animal has widely differing impacts on the sward structure of grassland. Large-scale cattle grazing in Georgia led to a mosaic of grassland, scrub, and trees, offering habitats for several highly specialized species of Orthoptera (Bontjer and Plachter 2002). However, contradictory evidence is provided by a study of vegetated sea wall flood defenses in the UK (Gardiner et al. 2015). On two cattle-grazed sea walls which had fairly short swards (<10 cm in height) with few grass tussocks, abundance of grasshoppers was lower than on the ungrazed sea walls which had higher densities and more variation in sward height (10–40 cm). This suggests that the impact of heavy cattle grazing, which leads to very uniformly short swards, is not favorable for Chorthippus grasshoppers which require tussocks of tall grass for shelter and feeding. However, on the sheep-grazed sea walls, which had greater variation in sward height (10–30 cm) than the cattle-grazed sections, abundance of grasshoppers was higher than in the ungrazed control swards which were quite uniformly tall and rank in nature (>40 cm in height). Therefore, the impact of grazing on grasshoppers is likely to be through the establishment of suitable sward heights at appropriate stocking rates, with light sheep grazing producing more variation in vegetation height than cattle grazing where swards can be uniformly short due to high stocking rates (Gardiner et al. 2015).

Fonderflick et al. (2014) found that that the impact of sheep grazing exerted a species-specific influence on the grasshopper assemblage, which varied greatly over the season in Mediterranean steppe-like grasslands. They concluded that extensive grazing by sheep tended to homogenize the vegetation structure and led to a temporary reduction in Orthoptera abundance at a pasture scale. Fonderflick et al. (2014) suggested that rotational grazing systems could conserve Orthoptera at a farm scale by promoting heterogeneity in sward structure. Irregular grazing, likely to produce a sward with greater sward heterogeneity, was also found to have significantly higher species richness of Orthoptera (28 species) than plots with mown grass (17 species) or permanent sheep pens (14 species) (Fabriciusová et al. 2011). Species-specific responses to grazing were also noted in submontane pastures in the Hrubý Jeseník Mountains in the Czech Republic, where the abundance of Gomphocerippus rufus increased substantially with grazing, which contrasted with G. rufus’ negative response to mowing (Rada et al. 2014).

In subalpine pastures in the Swiss Alps, Spalinger et al. (2012) found no direct effect of wild ungulate grazing (red deer and chamois). However, they did observe the small-scale alteration of habitats and plant N content by ungulates, which in turn affected Orthoptera abundance and diversity.

Intensive grazing by unmanaged wild rabbit, Oryctoloagus cuniculus, populations in Epping Forest in the UK, led to the extirpation of O. viridulus, a grasshopper with a preference for tall grassland (Gardiner 2010). The grazing created a very homogenously short grassland sward resembling a ‘lawn’ which consequently did not provide the necessary shelter or ‘cool’ microclimate for O. viridulus.

In Europe generally, there has been a move away from traditional sheep and goat farming to cattle grazing, leading to fewer and larger farms, with overgrazing a significant issue (Hochkirch et al. 2016). While this process was well underway during the middle of the 20^th century in north-west Europe, it has now spread to Mediterranean areas and the new Member States of the eastern European Union.

The effect of agricultural improvement of grasslands on Orthoptera has received little attention when compared to other aspects of farmland management in Europe in particular. One study detailed the effects of fertilization on the species composition and abundance of grasshoppers in the Netherlands (van Wingerden et al. 1992). In this study, overall grasshopper density and species richness decreased with increased fertilization, perhaps due to the higher herbage biomass and denser structure of the sward in the fertilized plots which created a ‘cold’ sward, unsuitable for diurnal activities such as basking of nymphs/adults or egg development.

The studies conducted by van Wingerden et al. (1991a, b, 1992) in the Netherlands, and research in the UK by Clarke (1948) and Gardiner et al. (2002), would seem to suggest that herbage height and biomass are important factors that regulate the abundance of grasshoppers in grasslands. Based on these studies, we would expect management which reduces herbage biomass to affect grasshopper abundance as outlined in the simple conceptual model in Fig. 5. The model attempts to portray the highly complex relationship between management which reduces the standing crop, and grasshopper abundance, in a simplified manner.

This model illustrates that lack of sward reduction management leads to higher herbage biomass, which, in turn, leads to a ‘cold’ microclimate and lower grasshopper abundance. This trend can be exacerbated by fertilizer input and high rainfall, which would both contribute to an increase in herbage biomass. Alternatively, sward reduction management actions such as grazing, mowing, and burning, can be expected to lead to low herbage biomass, a warmer microclimate, and higher grasshopper abundance. This, in turn, can be exacerbated by low rainfall in a certain year (Fig. 5).

Any research into the temporal changes in Orthoptera communities in agricultural habitats should consider the economic constraints of agricultural management. The primary objective of grassland farming, which accounts for approximately 66% of land use in the UK, is to produce high livestock yield to serve the consumer food chain (McInerney 1995). This is often produced through optimizing grass yields with the application of nitrogen fertilizer which may be detrimental to grasshopper abundance (Fig. 5).

Fig. 5. 

A simplified conceptual model of the possible effects of management to remove herbage biomass and lack of management on grasshopper abundance (the effects of fertilizer input and rainfall are added to provide a more holistic approach) (after Gardiner 2009).

A study of intensive and extensive pasture in the UK (Gardiner 2009) showed that unfertilized extensive pastures led to enhanced species richness, assemblage diversity and increased nymphal and adult abundance of Orthoptera, particularly of the grasshopper species C. albomarginatus and C. parallelus. These results supported those of Kruess and Tscharntke (2002) and van Wingerden et al. (1991a) who concluded that species richness and abundance of Orthoptera, respectively, were higher on extensively-grazed pastures compared with intensively-managed grassland. Contradictory evidence was provided by Batáry et al. (2007), who found only marginally significant differences in the abundance of Orthoptera between intensively and extensively grazed grasslands in the Hungarian Great Plain. Other studies on the impact of extensive grazing on grasshoppers in Europe concluded that grasshopper diversity and abundance were higher at grazed sites compared with mown grasslands (van Wingerden et al. 1991a, Wettstein and Schmid 1999).

The intensively managed pasture in Gardiner (2009) may have been unfavorable for Orthoptera due to silage cutting during June and intensive (high stocking rate) grazing. Inorganic fertilization led to tall vegetation height in May which can create a ‘cold’ microclimate (low temperatures in intensive pasture) that is unsuitable for nymphal development or post-diapause development in the egg stage.

Assemblage diversity of Orthoptera was higher in the extensive, unfertilized pastures perhaps due to the presence of tussocky patches of grass in rejected areas created where dung was deposited (Gibson 1997). Rejected areas were not necessarily present in the intensive pasture due to the removal of most vegetation above 70 mm during silage cutting and subsequent heavy grazing. In the extensive pastures, rejected areas supported small populations of bush crickets (Conocephalus discolor and Metrioptera roeselii) and grasshoppers (C. albomarginatus and C. parallelus). The short vegetation between tussocks provided ideal ‘warm’ conditions for basking and development of nymphs, while the tall vegetation offered shelter from inclement weather and avian predation as well as feeding resources. It is possible that grasshopper species such as C. parallelus actively seek out these nutrient rich niches in extensive patches (Gardiner and Hill 2004, Gardiner 2015), and may have to move between tussocks in a season due to disturbance by cattle or sheep and subsequent removal of tussocks through defoliation (Gibson 1997).

Examination of the stocking rate in the extensively managed pastures showed they were continuously grazed at approximately 2–4 cows per ha. The stocking rate suggested by Crofts (1999) as favorable for conservation objectives is 2 cows per ha for a similar grazing duration (24 weeks). Gardiner (2009) decided on a higher intensity stocking rate than is indicated by the literature to test whether a more economically viable grazing system with a higher number of livestock per unit area could provide biodiversity benefits. Although both extensive pastures provided better habitat for Orthoptera than intensively managed grassland, the suboptimal sward heights (<100 mm) led to low orthopteran densities, particularly of grasshopper species such as C. albomarginatus and C. parallelus. A lower stocking rate (2 cows per ha) would have led to a relaxation in the grazing pressure (Frame 1992) and taller sward height, particularly in July and August. These swards may have provided a greater chance of refuge for adult grasshoppers and bush crickets. However, a trade-off must be considered between economic viability of the grazing system and biodiversity benefits. Since the extensive pastures provided larger numbers of Orthoptera and higher assemblage diversity than the intensive sward, the moderate-intensity stocking rate and grazing pressure were justified on financial grounds. The stocking rate of 2–4 cows per ha is only slightly lower than that suggested by Frame (1992) as the proper management of improved swards for optimal agricultural production (5–8 cows per ha). Pastures are often assessed by using target sward heights and, for improved grassland managed by continuous grazing, the target sward height is 60–80 mm for cattle (Frame 1992). In all years the extensive pastures had a mean sward height that was predominantly 60–90 mm, suggesting that they were managed at stocking rates which produced swards of acceptable height for good agricultural management.

The absence of inorganic fertilizer input on these swards may impact upon yields but not necessarily economic viability. For example, under silage cutting, inorganic fertilizer input may substantially increase dry matter (DM) production in grass/swards (Frame 1992, Tallowin et al. 2002) but beef cattle output on low input systems (restricted N input) and fertilized pastures (moderate N input) has been found to be very similar, suggesting that low input systems may not affect the economic viability of grazing, particularly in clover-rich swards [such as the extensive pasture in Gardiner’s (2009) study] with high rates of nitrogen fixation (Frame 1992). Other studies confirm that absence of fertilizer input may not necessarily affect animal liveweight gain and may be comparable to conventional farming systems with a high nitrogen input (296 kg N per ha; Lawes et al. 1995). However, lack of inorganic fertilizer usage in the study of Lawes et al. (1995) did significantly reduce the quantity of herbage conserved, suggesting that silage cutting may not be viable on extensive pastures. The absence of silage cutting and fertilizer input on pastures would seem to be a key requirement for maintaining populations of Orthoptera, and we suggest that where conservation of insects such as grasshoppers and bush crickets is desired, then pastures should be managed by continuous, low-input grazing at a moderate stocking density (2–4 cows per ha) which produces a sward of 60–80 mm in height. A study of extensive pastures by Marriott et al. (2002) concluded that unfertilized herbage at a height of 80 mm with a high quantity of dead leaf material may not pose problems for livestock diet due to preferential grazing of green leaves.

Of course, the stocking rates and choice of livestock are greatly influenced by subsidies provided by governments or the Common Agricultural Policy (CAP) in Europe, for example. Many farmers in the EU receive payments to farm more sustainably.