Is livestock grazing a key factor for changing vegetation patterns in lime rich coastal dunes in the Netherlands?

Abstract

In 1990, livestock grazing was introduced in Meijendel, a 1800 ha lime-rich coastal dune area, at a density of 0.06-0.07 LLU. ha-1. year −1 (1:12-18 ha) to counteract encroachment of tall grasses and shrubland on dune grassland and increase the bare sand area. Monitoring was based on four digital orthophotos (1975-1990-2001-2009) with a high spatial resolution (pixel size 25 × 25 cm). The changes were tested using Generalized Estimating Equations. Habitat changes occurred, but contradicting our hypothesis, there was no significant impact from the grazing on bare sand, grassland or shrubland within 11 and 19 years post livestock introduction. (1) After several decennia of decreasing bare sand, there was a significant increase between 2001 and 2009, irrespective of livestock presence. (2) The changes in grasslands and shrublands are independent of the livestock, but dependent on distance to the coast. (3) Bare sand and shrub cover determine the space left for the dune grasslands. It appears other factors than livestock grazing must have induced the changes. Changes in climate conditions and nitrogen load might have stimulated bare sand. An interaction with the end of Marram planting in 1990 cannot be concluded from available data. The disease-led reduction of rabbit grazing from the mid-1950s led to an expansion of the dominant shrub Hippophae rhamnoides. However, Hippophae shrubland typically regresses to grasslands on its collapse after 25-40 years. Tree species like Crataegus, Betula and Quercus will gradually dominate the landscape for far longer. Active removal of these indigenous species is necessary to prevent future loss of dune grasslands.

Rabbits rule : evaluating livestock grazing in coastal sand dunes of Meijendel, the Netherlands

“…2) are in line with Van der Hagen et al (2020a, 2020b showing changes in the area of forests in 1,900 ha of Meijendel in the years 1938,1966,1983 and 2014 (see Van der Hagen et al 2020b). On the other hand, regressive succession has manifested itself after an increase of blowouts with bare sand since 2001 (Aggenbach et al 2018;Van der Hagen et al 2020a). The impact of these changes can also be seen in the re-occurrence of the Phleo-Tortuletum in a few permanent plots.…”

“…The hypothesis on livestock stimulating bare sand could not be tested in the permanent plots, because there are no ungrazed controls located next to the permanent plots. But the fact that the open Phleo-Tortuletum returned in the permanent plots, even in the grasslands with acidic topsoils in 2004 and from 2008 onwards, is in line with the reality of an independently caused and general increase in the number of blowouts from 2001 onwards (Aggenbach et al 2018;Van der Hagen et al 2020a).…”

“…It is considered that the 1954 outbreak of myxomatosis and the 1989 outbreak of RVHD-1 is more likely to explain the observed shift in progressive succession. All in all, rabbits seem to be the crucial factor in these changes ( Van der Hagen et al 2020a, 2020b.…”

Blowout Morphometrics and Mass Balances

“…Off-road vehicle disturbance, pathway trampling, and poor land-use practices can remove anchorage vegetation facilitating blowout genesis (Hesp et al, 2010;Acosta et al, 2013;Houser et al, 2013;Jewell et al, 2014). Pastoral farming poses a dual threat of increased grazing pressures as well as high-intensity trampling involved with moving livestock between paddocks (Blanco et al, 2008;van der Hagen et al, 2020). Indirectly, infrastructure projects and urbanisation may also divert wind patterns, changing the spatiality of sand transport mechanisms and influencing the formation of deflation landforms (García-Romero et al, 2019;Wernette et al, 2020).…”

Coastal Vulnerability Index revisited: a case study from Maricá, RJ, Brazil

“…The concept of vulnerability addresses possible impacts and consequences that a particular environment would suffer under an extreme event, and involves an integrated analysis of social, economic and natural factors (ZOU; THOMALLA, 2008;IPCC, 2007;DOLAN;WALKER, 2003;FRAZIER et al, 2010). However, there are studies that concentrate on estimating vulnerability through a more physical bias, using geological, geomorphological and oceanographic parameters (ABUODHA; WOODROFFE, 2006;MUSEKIWA et al, 2015;SZLAFSZTEIN;STERR, 2007, PALMER et al, 2011TRAN et al, 2010;DEVOY, 2008). This dichotomy between physical and human aspects hinders the definition of a standard methodology, and an individual approach of each study area should be designed, trying to prioritize the main demands of each environment: in a coastline that has high populational density, human aspects should have a greater relevance, whereas in a sparsely populated coast, an analysis that prioritizes the physical aspects is preferable.…”