Malo Arrazola, Juan Esteban

Peco Vázquez, Begoña

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Extensive Cereal farming^ steppes and dry grasslands in Spain : ecosystems on the brink Juan E. Malo & Begoña Peco. Dpto. Interuniversitario de Ecología. Universidad Autónoma de Madrid. E-28036 Madrid. Spain. FAX: 34 m-^ w^ íüüü;' ES RENCONTRES DE UAGENCE REGIONALE POUR L'ENVmONNEMENT PRO VENCE-ALPES-COTE D'AZUR Abstract Extensive cereal fanning, dry grasslands and steppes occupy large áreas of Spain (c.a. 4,500,000 ha) and they have a great natural valué due to animal and plant species living in them. The.origin and maintenance of open lands are so closely linked to traditional exploitation that the future of many of their most t>pical spe-cies is tied to that of man-induced spatial diversity. Thus, socioeconomic changes in rural áreas during last decades have already modifíed the dynamics and struc-ture of these landscapes. The short- and medium-term prospects for the agradan sector include the potential for dramatic changes to them. Tlie replacement of tra-ditional management by intensive exploitation, tree plantations or even the complete abandonment of farming acti-vities, would have a fatal impact on the plant and animal components of the eco-system and their interactions. In this context, any conservation policy must safeguard these landscapes by maintai-ning a sufficiently large área and diversi-ty of agradan substrata. Extensive cereal farming, steppes and dry-grasslands (pseudo-steppes hereaf-ter) cover large áreas of Spain (Suárez 1994, Suárez et al. 1992, 1995). Steppes with natural vegetation (in remaining tracts of at least 300 ha) have been calcu-lated to cover 570,000 ha, while the total surface área of pseudo-steppes is approximately 4.5 million ha. Some esti-mates, however, raise this to 10 million ha. Natural-vegetation steppes are com-prised of a series of distinct plant com-munities, some of which are included in ihe Habitats Directive under the 'Salt and gypsum steppes', 'Pre-steppic sclerophyl-lous scrubs' or 'Dry grasslands and steppes' headings. All of these communi-lies can be found in isolation, but more often they are an integral part of the farm l a n d s c a p e s d i s c u s s e d h e r e . Spanish pseudosteppes are highly valuable due to the number of species whose populations rely almost exclusive-ly on them (Suárez et al. 1992). Many of their plant species are endemic (e.g. Gypsofila spp., Thymus loscosii, Boleum asperum, Vella pseudocytisus subsp, pseudocytisus and paui), and they also host relie populations of species whose distribution centres are very distant (e.g. Krascheninnikovia ceratioídes, widely distributed in Asia and with small popu-lations in Morocco and the Ebro Depression, IXíA 1994). Bird conmiuni-ties in Iberian pseudo-steppes are also extremely valuable (Tucker & Heath 1994). They include two species whose populations are vulnerable at world-level (Otis tarda and Falco naumanní) and another near-threatened (Tetrax tetrax), Moreover, 15 out of the 17 most charac-teristic European steppe bird species are amongst the Species of European Concera (SPECs), and 14 of the fonner have their biggest populations in Spain. This feature is critical, as one is conside-ned endangered, 5 have declining popula-tions, 6 are vulnerable and one is defined as rare (Tucker & Heath 1994). The natural valué of pseudo-steppes is closely linked to their historie use. Open landscapes, while natural on the Iberian Península, probably occupied smaller áreas prior to human deforestation for agriculture and livestock husbandry (Costa et al. 1990). The gradually increa-sing área of pseudo-steppes and the far-ming systems developed in them permit-ted the adaptation of animal and plant communities, thus giving rise to high-diversity ecosystems (Aschmann 1973). Traditional land management was based on cereal and legume cropping combined with one- to eight-year fallow periods. Pasture and scrub occupying shallow soils and slopes were traditionally pre-ser\'ed, and intenningled with arable land for sheep grazing, the same use given to fallow land and stubble. Under this management, unculüvated land acted as a refuge for many species, while the increase in open áreas and the ensuing spatial diversification led to the increase in species adapted to these landscapes. The cióse relation between exploitation and conservation is the major threat to pseudo-steppes. Socio-economic changes associated with the rural crisis (especially since 1960) started the decli-ne of these landscapes and their animal and plant populations (González-Bemáldez 1991, Peco et al. 1993). The low productivity of many farms, the increase in transpon facilities and the demand for an mban workforce led to massive emigraticHi and the alteration of traditional management systems. Similar changes (but on a larger scale) due to the universalization of the economy and the Common Agriculture Policy crisis can be expected in the short term, Changes in management have foUowed an Intensify or abandon' rule, with effects at different spatial scales. Large áreas have become completely depopula-ted and all cultivation suspended, while other áreas have multiplied their produc-tivity through the use of more powerful machinery and agro-chemicals, as well as to fann enlargement The same pro-cess has happened at much smaller scales leading to ¿te partial depopulation of vil-lages and the mixture of intensive far-ming and abandonment in most agrarian landscapes (Peco et al. 1993). Thus, cul-tivation has been modemized and restric-ted to the more productive soils (e.g. val-ley floors), now surrounded by unplou-ghed fíelds. Livestock has become par-tially enclosed and supplemented with fodder, and traditional herd shifting in search of pastures has ceased. In spite of these measures, profitability remains very low in many áreas: mean cereal crops average 2,500 kg/ha and their interannual variability due to weather is very high. Stocking rates are usually lower than 1 sheep/ha, although 2-3 sheep/ha is achieved in some áreas thanks to supplementary fodder. Such changes have led to a constant decline in both the área of fallow land 179 COLLOQUE BIO'MES 1995 aiicl the diversity of land uses. As a direct consequence, the potential área for step-pe species has diminished which may be the reason for the present 'vulnerable', 'declining' or 'endangered' status of many of them (Tucker & Heath 1994, DGA 1994). Other factors such as the increase in pesticide use may have also had nega-tive effects on animal and plant popula-tions. At present, low profitability is combining with an ageing population and small farm sizes to destabilise the system, and the 'intensify or abandon' rule will soon modify large áreas of the territory. The maintenance of present farms is unviable as it is mostly dependent on subsides from the European Union (Peco et al. 1993). The crisis in tlie agriculíural pro-duct-prices policy and the uncertainty about its future make any landowner death or retirement lead to the abandon-ment of the farming use of a part of the territory. Thus, CAP subsides and other land-use policies can lead to dramatic changes in farm áreas, as happened during 1990-91 and 1991-92 with sub-sides for sunflower crops (663,000ha and 1,456,000 ha respeciively vs. 2,000 ha in 1989-90). Afforestation programmes implemented under the R. 2089/92/CEE are a good example of tliis, and are pro-bably the biggest threat to pseudo-steppes as they can affect large áreas and many landowners see them as a means of getting income from their proprieties. The consequences of such changes are difficult to evalúate, but the losses of área and diversity of agrarian substrata may have direct effects on plant and animal populations. New tree plantations or irri-gation over large áreas can lead to the^ extinction of some species (e.g. Puccinellía pungens (Poaceae) or Eucypris aragonica (Ostracoda) endemic to salt ponds) as well as to the decline in potential áreas for all steppe organisms. The spatial simplification of plant com-munities in landscapes can also be detri-mental to animal species as many of them rely on the combination of different , agrarian subsü*ata (Tellería et al. 1988). The indirect consequences of changes in land use may be even greater, as altera-tions to ecological processes can reinfor-ce the declining trend in steppe species. Acknowledgements This is a very difficult point to analyze, but empirical data show íhat grazing ces-sation, tlie increase in some species due to changes in farming methods and the alteratíon of physical processes can have serious effects on typical open land spe-cies. An analysis of other processes would undoubtedly genérate a longer list of threatening side effects associated witii land-use changes. The elimination of livestock changes competitive relations among plant spe-cies and facilitates succession towards communities with bigger plant develop-menL Such successional stages are cha-facterized by the dominance of woody species, a decrease in small-scale plant diversity and the displacement of species associated with disturbance (Grime 1979, Tilman 1988, Peco et al. 1993). Many endemic or relie steppe plant spe-cies (i.e. Sysimbrium cavanillesianutii, Krascheninnikovia ceratíoides) are somewhat ruderal and their maintenance is associated with some degree of distur-bance. Thus, they could be displaced by 'competitive species' following tlie remo-val of grazing. Moreover, livestock is a powerful seed disperser (Sorensen 1986, Malo & Suárez 1995), and it thus may help to maintain plant populations. Long-range seed dispersal may be a key factor controlling diversity in open lands as plant populations seem to be affected by local colonization-extinction processes due to habitat diversity and random events (Kadmon & Shmida 1990). The lack of dispersal has been blamed for the species impoverishment found in some áreas following grazing cessation (González-Bemáldez 1991), and the importance of sheep flocks as seed vec-lors has been postulated for some ende-mic species (i.e. Boleum asperuní, Vella pseudocytisus, DGA 1994, F. Domínguez pers. com.) Succession towards woody plant com-munities, the establishment of small forests among crops and the abandon-ment of traditional farming can lead to an increase in opportunist predators. Tliese species may become a major tlireat to ground-nesting steppe birds. Very high nest predaüon rates have been found in and around forested plots on pseudo-steppes in Central Spain (Santos & Tellería 1992, J. Herranz, pers. com.). Also, nest predation by foxes and feral dogs has been found to make lark popu-lation breeding unviable in one Natura Reserve in southeastem Spain (Suárez et al. 1993). Finally, the disturbance of watershed levéis following irrigation implementa-tion may cause the desiccation of ephe-meral ponds (followed by ploughing) or changes to their chemical and seasonali-ty characteristics. As many endemic and relie steppe taxa on the Iberían Península are associated with these environments (i.e. DGA 1994), both alterations may lead to species extinctions. Due to the above-mentioned detenni-nants, traditional conservation schemes are not directly applicable to these áreas. The cost of preserving traditional far-ming Systems over such large áreas makes policies based on farm subsides or Protected Áreas unsustainable. Also, agro-environmental regulations from the EU may have a low level of acceptance as intensiñcation or tree plantation can be more profitable. Thus, the preservation of the current sur-face área of pseudo-steppes cannot be achieved, and conservation strategies should be aimed at maintaining their major characteristics. They should focus on preserving áreas ihat are large enough to ensure the survival of plant and animal populations, but they should also pay special attention to the spatial diversity at different scales of the resulüng land-scapes. Such a combinaüon of área and spaüal diversity should sustain ecologi-cal processes. Prior to the design of such strategies, it is urgent to improve our understanding of species refuges, species habitats and the use of different landsca-pe patches, and the processes linking them. All of this knowledge should be a basis for a spatial design in which áreas of natural vegetation are kept intennin-gled with crops and stubble in a somew-hat similar fashion to tradiüonal sys-tems. If this were possible, modem inten-sified exploitations could be valuable for the maintenance of steppe species, and the preservation of pseudo-steppe land-scapes would be achievable on economic as well as ecological grounds. Most of the ideas presented here are tlie result of work and discussion among members of the Land Ecology section of our Department. The Botany Department at U.A.M. kindly lent us some unpublished work, and Catherine Levassor translated the abs-íract into French. 180 COLLOQUE BIO'MES 1995 Bibliography ASCHMANN, H. 1973. Man's impact in several regions with Mediterraiiean climate. In: di Castri, F. & M(X)ney, H.A. (eds.) Mediterranean Type Ecosystems Origins aiid structure. Springer-Verlag. Heidelberg. pp 363-372. COSTA, M.; Gaicía, M.; Moría, C. & Sainz, H. 1990. La evolución de los bosques de la Península Ibérica: una interpretación basa-da en datos paleobiogeográfícos. Ecología (Fuera de Serie) 1: 31-58. DGA, 1994. Bases técnicas para la protección de la flora amenazada de Aragón. Informe del Dpto. de Botánica de la U.AM. oara la Dirección General de Aragón, (in press). GONZÁLEZ-BERNÁLDEZ, F. 1991. Ecological consequences of the abandonment of traditional land use systems in Central Spain. Options Méditerranéennes. Serie Séminaires 15: 23-29. GRIME, J.P. 1979. Plant strategies and vegetation processes. John Wiley & Sons. Chichester, U.K. KADMON, R. & Shmida, A. 1990. Spaüotemporal demographic processess in plant populations: A mathematical approach and a case study. Am. Nat. 135: 382-397. MALO, J.E. & Suárez, F 1995. Herbivore maininals as seed dispersers in a Mediterranean 'dehesa'. Oecologia PECO, B.; Suárez, F; .Timénez, B.; Herranz, J.; Malo, J.E. & Levassor, C. 1993. Recomendaciones para la gestión y conservación del medio natural frente a los cambios asociados con la Política Agraria Comunitaria. Informe ICONA-U.AJví. (unpublished). SORENSEN, A.E. 1986. Seed dispersal by adliesion. Ann. Rev. Ecol. Syst. 17: 443-463. SANTOS, T. & Tellería, LL. 1992. Edge effects on nest predation in Mediterranean fragmented forests. Biol. Cons. 60: 1-5. SUÁREZ, F 1994. La protección de las estepas mediterráneas. Directrices generales para la propuesta de una estrategia de conser-vación. Doc. XI/153/94. Dirección General XI, Medio Ambiente, Seguridad Nuclear y Protección Civil. Comisión Europea. SUÁREZ, F; Sainz, H.; Santos, T. &. González-Bemáldez, F 1992. Las estepas ibéricas. Unidades Temáticas Ambientales. Ministerio de Obras Públicas y Transportes. Madrid. SUÁREZ, F: Yanes, M.; Herranz, J. & Manrique, J. 1993. Nature reserves and the conservation of Iberian shrubsteppe passerines: the paradox of nest predation. Biol. Cons. 64: 77-81. SUÁREZ, F; Herranz, J. & Yanes, M. 1995. Conservación y gestión de estepas. Actas del Simposium para la Conservación de las Aves Esteparias y su Habitat. Valladolid. (in press) JTELLERÍA, J-L.; Santos, T.; Alvarez, G. & Sáez-Royuela, C. 1988. Avifauna de los campos de cereales del interior de España, In: Bemis, F (ed.) Aves de los medios urbano y agrícola en las mesetas españolas. Monografías de la Sociedad Española de Ornitología. N^ 2. Madrid, pp: 173-319. TILMAN, D. 1988. Plant strategies and üie dynamics and structure of plant communities. Princeton Monographs, Nr. 26. Princeton, U.S.A. TIJCKER, G.M. & Heath, M.F 1994. Birds in Europe. Their conservation and status. Birlife Conservation Series no. 3. BirdLife International. Cambridge, U.K. Resume Cultures céréaliéres extensives, steppes et páturages xérophytiques en Espagne: écosystémes en suspens. Les cultures céréaliéres extensives, les páturages xérophytiques et les steppes occupent une importante superficie en Espagne (dans son ensemble environ 4,5 millions d' Ha), et possédent une grande valeur naturelle, conséquence d'une grande richesse en plantes et animaux. L'origine et le maintien de ees milieux ouverts se trouvent étroitement liées á leur utilisation traditionnelle; ainsi la consen'ation des espéces les plus caractéristiques dépend de la diversité spatiale créée par les aménagements humains. Les chan-gements socio-économiques survenus en milieu rural ees demiéres décades ont affecté la structure et la dynamique de ees paysages. Les perspectives á court et moyen tenne font craindi-e des changements encoré plus drasüques. L'abandon de Fexploitation tradi-tionnelle pour des systémes plus intensifs ou la substítution par des cultures arborées, voire l'arrét complet d'activités agraires, peu-vent avoir de graves consequences sur la faune, la flore et les processus caractéristiques des milieux ouverts. Dans ce contexte, la mise en place d'une politique de conser\'ation p^ isse par la sauvegarde de grandes zones de paysages diversifíés. 181 ANNEXES Original landscapes Traditionaf Exploitation PSEUDO-STEPPES Rural Abandonement Crisis Intensificatlon Plant succession Timber forests . Increase in exploitation slze . Use of agrochemicals . Crop changes . Irrlgation . Woody crops . Enclosed livestock raising Regional and local effects i . Loss of pseudo-steppes extent . Diminution of spatial diversity . Alteration of interespecific interactlons Fig. 1 : Major factors determinig Spanish pseudo-steppes present and future 182 ANNEXES Picture 1 : Traditional pseudo-steppe landscapes wre composed by a mixture of natural vegetation and clops , . . . , - . \ . - . ...v.'?*'^Y''f^^- .MX-^ ^^ Picture 2 : Lax productivity, cereal clops are not profítable anymore and they are thos abandoned yA%«^^^.^^^^^^^^^^^v.^^y.•^:i•^.•^^^^^v.^^^^^•>.s•^,v^.•<,^v•'.%%^v.v<X^^•. mm Picture 3 : Landscapes are changing following tlie «intensity or abandon» : irrigation projects and intensive livestock - raising threat the conservation of dry grasslands J 183 

Extensive cereal farming, steppes and dry grasslands in Spain: ecosystems on the brink

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Extensive cereal farming, steppes and dry grasslands in Spain: ecosystems on the brink

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