Sustainable Management of Coastal Dunes to Preserve Biodiversity

Proposal Abstract

This study aimed to:

1. Determine the impact of woody vegetation cover removal on the rates and patterns of re-establishment by native, sand-dwelling organisms (plants, arthropods, reptiles, and small mammals) and on the interactions between them.
2. Determine the optimal plant cover that will simultaneously facilitate sand mobility and high sand-dwelling biodiversity.
3. Create a data set of sand dune dwelling arthropods and thereby contribute to an understanding of the biodiversity of dune ecosystems.
4. Determine the potential for using specific soil-dwelling arthropods as indicators of habitat biodiversity in dune systems.
5. Suggest the optimal management tools to preserve the Nizzanim Nature Reserve coastal sand dunes.

The study was conducted during 28 months (May 2004-October 2006) and included 10 field excursions. The observed taxa were: plants, arthropods, rodents, and reptiles. Twenty two dunes were selected in the area of Nizzanim Nature Reserve that present 3 typical dune types, concerning their stabilization level: 3 non-stabilized dunes (marked as "A"), 6 semi-stabilized "B" and "C") and 8 stabilized ("D"). The vegetation from 6 stabilized dunes and one semi-stabilized dune was removed by bulldozers on April 2005 (4 dunes were manipulated to "A" and 3 dunes to "B-C"), and the expeditions that followed started to monitor the changes in the vegetation and animals following the experimental land management. Capturing and observation methods differ among taxa. The results indicated that:

Vegetation

1. Stabilization process changes the herbaceous species composition. The herbaceous community on the stabilized dunes differs significantly from that on the non‑stabilized and semi-stabilized dunes.
2. The relative number of psammophilic species decreases with dune stabilization.
3. The number of herbaceous species and their coverage increases with stabilization, although the size of the open area decreases. This might be due to better soil conditions (organic content and soil moisture) on the stabilized dunes ("open patch area – soil conditions" trade off).
4. Species beneath shrubs on the stabilized dunes differ from those in the open.
5. Spatial heterogeneity (expressed in dune types) increases landscape diversity.
6. Removal of shrubs from stabilized dunes: (a) does not turn the herbaceous community into communities that were observed on the non-stabilized and semi-stabilized; and (b) increases herbaceous species number and coverage (c) increases psammophilic species number and coverage, but not their relative contribution to the plant community.

Arthropods

1. Plant cover shapes the community structure of sand dune arthropods.
2. Plant cover does not change the overall density and species richness of arthropods, however, there is a strong species turnover between the dunes.
3. There is a clear distinction between the assemblage of shifting sand dunes and stabilized dunes. On shifting sand dunes most species are from arid-psammophile distribution, while on stabilized dunes we find generalist species that have a mesophilic distribution.
4. There are species with high affinity to non-stabilized and semi-stabilized dunes that can be used as bio-indicators for shifting dunes. If the current rate of stabilization will continue we will lose species that specialize on shifting sand dunes. Species like Mecynotarsus bison and Scarites striatus that are absent from dunes with plant cover higher than 20% will be lost first and then we will lose species like Eurocalus henoni that are present even at 30% plant cover but disappear at higher plant covers.

Rodents

1. There is a gerbil species that can be found only on the non-stable dunes as well as a different species on the stabilized dunes. Both species are found on the semi-stabilized dunes.
2. The highest species richness exist on the semi-stabilized dunes
3. Re-establishment of psammophile species may be accelerated on manipulated dunes that are adjacent to non-stabilized dunes ("source").

Reptiles

1. Different lizard species have different affinities to dune stabilization level.
2. Evidence and observations of snake activity are scarce in comparison to the lizards An alarmingly small amount of evidence was found of the monitor Varanus griseus, probably the species most directly threatened by degradation and development of the coastal sand dunes over the last decades
3. There are trends of increasing similarity, with time, between the manipulated plots and the reference plots (non-stabilized or semi-stabilized sands).

Since massive human disturbances are occurring in almost the entire coastal line of Israel, the future of psammophile species of the area depends on the fate of the Nizzanim Reserve. Species that have a psammophile distribution, i.e. restricted to sandy habitats, will disappear if Nizzanim is not managed in a correct way. Most of these species are found in shifting sand dunes (e.g., Scarites striatus, Cymindis andreae, Mecynotarsus bison, Amblyderus sabulosus Eurycaulus henoni, Scaurus puncticollis, Stenosis dilutipes, Dendarus piceus, Tentyrina orbiculata) and, therefore, it is those dunes that should be mostly protected and even turn the stabilized dunes into shifting ones. However, there are some species (Graphopterus serrator) that are psammophile and require the stabilized dunes.

These results support the idea that the best management of the Nizzanim Sand Dunes in order to maintain biodiversity is to maintain spatial heterogeneity at least at two scales. At the larger scales, we need both habitat types: stabilized and shifting sand dunes to support both assemblages. At the smaller scale, it is recommended to maintain both microhabitat types in each dune since most species need both of those patch types. It is therefore recommended to remove shrubs from some dunes that are beginning to be stabilized (semi-stabilized), but to leave behind several patches with shrubs. The overall guideline is to create shrub removal to 10% plant cover.

The findings obtained from both rodents and reptiles suggest that future attempts to treat semi-stabilized and stabilized dunes should concentrate in areas that are still connected to shifting dunes with suitable habitat for pasmmopilic species. Areas that are too isolated for transfer of certain animals and plants may require active transfer of a few individuals to establish new populations on isolate treated dunes. Nevertheless, any such attempts will need to be monitored for several years, because we need to observe the impact of plant removal after at least 3-4 years to evaluate the utility of the treatment.

We still have a long way to go in order to answer the question: Will we fully rehabilitate the non-stabilized and semi-stabilized communities on stabilized dunes in which the woody vegetation was removed? However, our results indicate that large scale operations like our removal of vegetation need to be monitored for a long period of time and by using additional and sustainable methods, such as grazing, in order to keep lower vegetation cover on stabilized dunes and semi-stabilized dunes.

Outcome

No outcomes reported

Funding