Effects of abandoning long-term goat grazing on species composition and species richness of pastures at La Gomera, Canary Islands

Abstract

Goat grazing management is a powerful ecological force structuring plant communities which effects are highly different depending on factors such as climatic conditions, grazing intensity, type of plant community, etc. Pastures in the Canary Islands have important heritage, socioeconomic and landscape values because they are the remains of traditional livestock management and a key element of local economy. An experimental study of goat grazing exclusion has been carried out in an area of La Gomera Island to determine the main effects of grazing abandonment on species richness and species composition. The species composition of La Gomera pastures is more sensitive to grazing than to climatic variability, though effects in the species richness in relation to grazing were not detected. Because the pasture origin in this area involved artificial, removing of non useful plants in order to provide land for agriculture more than 300 years ago, and using it for pastures around 80 years ago, the sustainable use has maintained this rich plant community. Grazing abandonment can have a negative effect on the pastures' diversity, as grazing has been a strong force in the maintenance of certain species. Public promotion of this primary activity is suggested to allow the continuation with minimal effects on the vegetation composition. This will help to conserve the high diversity of this area and the promotion of natural values as well as traditional and sustainable human activities.Additional key words: detrended correspondence analysis; plant community; rarefaction; sustainability. Resumen Efectos a largo plazo del abandono del pastoreo de cabras en la composición y riqueza de especies en los pastizales de La Gomera, Islas CanariasEl pastoreo caprino es una importante fuerza estructurante de las comunidades de plantas, con efectos altamente dependientes de factores como las condiciones climáticas, la intensidad de pastoreo y el tipo de comunidad entre otros. Los pastizales de las Islas Canarias tienen valores culturales, socioeconómicos y paisajísticos importantes, puesto que son remanentes de actividades tradicionales y elementos clave de la economía local. Se ha llevado a cabo un estudio de exclusión del ramoneo de cabras en la isla de La Gomera para determinar los efectos del abandono del pastoreo en la riqueza y composición de especies de sus pastizales. La composición de especies de los pastizales está más influenciada por el pastoreo que por la variabilidad climática, aunque no se detectaron efectos en la riqueza de especies entre áreas pastoreadas y no pastoreadas. La explotación sostenible de estos ecosistemas para fines agrícolas desde hace más de 300 años y como pasto desde hace aproximadamente 80 años, ha mantenido su alta riqueza de especies. El abandono del pastoreo puede afectar negativamente a la diversidad de los pastizales, al haber sido una importante fuerza para el mantenimiento de ciertas especies. Se sugiere la promoción pública de esta actividad para asegurar su continuación con mínimos efectos...

Long‐term vegetation responses to different goat grazing regimes in semi‐natural ecosystems: a case study in Tenerife (Canary Islands)

“…Some researchers suggest that the maintenance of goat grazing is highly desirable for agroecosystem conservation (Arévalo et al. , ,b; Fernández‐Lugo et al. , ), while others argue that grazing is responsible for the degradation of plant communities and leads to endemic plant extinction (Nogales et al.…”

Goat grazing, its interactions with other herbivores and biodiversity conservation issues

“…Although invertebrate diversity increased in Volcán Alcedo (Galápagos) after a severe grazing by introduced feral goats which temporarily increased habitat heterogeneity, its conservation value was questioned, and the species naturally occurring in the scrub and groves, as well as others from humid open habitats, were expected to disappear unless the situation was reversed (Desender et al, 1999). Conversely, moderate goat grazing is considered valuable for the conservation of pastures dominated by native or endemic species in Tenerife Island (Fernández-Lugo et al, 2009), and negative effects on plant diversity are expected after goat grazing abandonment in pastures which sustain endemic plant species in La Gomera Island (Arévalo et al, 2011).…”

Effects of fertilization management on pasture productivity and nutrient composition

“…The impact of climate variability is one of the most relevant factors conditioning biomass or species composition and richness (Lauenroth and Sala, ; Arévalo et al ., , ; Fernández‐Lugo et al ., ), and our results are consistent with this. Other studies have found that the dominance of certain species groups is related to soil nutrient composition or soil seed‐bank composition (Arévalo and Chinea, ).…”