Reducing the fuel load of mountain heaths, heath-to-thorns and broom (up to 2 metres) is one of the key actions planned under the LIFE Maronesa project. In addition to the unconditioned consumption of grazing shrub vegetation by cattle, three techniques for reducing fuel biomass with direct human intervention are planned:
– Prescribed Fire
– Mechanical Shredding
– Consumption and trampling by cattle near movable feeders.
Right from the start of the project, the livestock farmers involved in LIFE Maronesa showed great interest in mobile feeders rather than the mechanical clearing of shrubland. The possible transfer of funds between the budget lines for clearing shrubland and the purchase of cattle feeders depends on the answer to a simple question: which of the two techniques is more efficient from a technical and economic point of view?
Economic analysis:
- Unit cost of shredding: 1281 €/ha.
- Unit cost of each feeder (Jourdain brand): 2000€
- Amortisation of a feeders (20 years of equipment, interest=4%)
- Use of the cattle feeder: 5 months/year, with 10 changes of location (stays of 15 days)
- Annual cost of the feeder: 2000/20×1,04+20×10=296€/year
- Cost of moving a feeder (40€/h tractor, 0,5h moving the manger): 40×0,5=20€
- Area consumed/ trampled at each feeder location (9m radius): 92×3,1415 = 0,026ha
- Area consumed/pastured annually around a feeder: 0,026ha x 10 location changes = 0,26ha/year
- Unit cost (ha) of shredding/ trampling with the feeder: 296/0,26 = 1138€/ha
At the following coordinates: 41°26’51.4‘N, 7°43’16.0’W and 41°26’49.09‘N, 7°43’16.27’W, using Google Maps, we can see the effect that the mangers have had on the landscape at the Casal da Bouça farm.
Technical analysis
Although the costs of the two alternatives are similar, the cattle feeders are technically superior:
– They protect the hay from the rain and allow more efficient use of this forage resource (compared to the alternative of ‘throwing the hay on the ground’);
– The distribution of hay in the mountains reduces the movement and energy expenditure of the animals (with reference to the distribution of hay in the lowlands, close to the cowsheds);
– They increase the permanence of animals on the mountain and the pressure of herbivory on shrub vegetation;
– They facilitate the dissemination of seeds of herbaceous meadow plants in the mountains (confirmed, for example, by the increase in the distribution area of Trifolium repens);
– The distribution of hay on the mountain implies a transport of nutrients up the mountain and therefore an increase in the stock of nutrients and their cycling within the mountain ecosystem;
– Increased disturbance by herbivory and nutrient stock and cycling promotes herbaceous vegetation in detriment of shrub cover with gains in useful forage production;
– Shredding, rather than herbivory, does not eliminate fine fuels (fire severity is correlated with the mass of fine fuels per unit area);
– A similar process occurs with the use of feeders in the lameiros (mudflats/hay meadows);
– The cattle feeders will continue after the LIFE Maronesa project (functional for at least another 15 years).
It should also be noted that the maintenance of the high-quality removable feeders (Jourdain brand) comes down to tightening screws on moving parts.
Conclusion
The unit costs of the two techniques (1281€ vs 1138€) are similar. The technical advantages contain economic gains not accounted for in the economic analysis. In the medium term, the manger option is technically and economically more favourable.