Good grazing management also means measuring its effects. The LIFE ScrubsNet protocol proposes assessing browsing by taking into account two key factors: the palatability of each species and its capacity to regrow. Based on the level of consumption and damage observed, it is possible to obtain a useful reference for adapting management and supporting the regeneration of the dehesa and shrub pastures.
Browsing is a normal part of vegetation use in extensive livestock farming. Cattle, sheep, goats and pigs may consume leaves, shoots and branches from trees and shrubs, but not all plant species respond in the same way to this pressure.
A highly palatable plant may be consumed quickly, while another species that is less attractive to livestock may only show significant damage when grazing pressure is high.
For this reason, the document “Livestock and scrub management for dehesa regeneration”, developed within LIFE ScrubsNet, proposes assessing the palatability of each species together with its capacity to regrow or resist grazing.
Two factors that help interpret browsing
The protocol organises species into different classes according to the combination of their palatability and their ability to recover after browsing.
Species with very high palatability and low regrowth capacity include, for example, narrow-leaved ash, wild olive, some broom species and brambles. Other species, such as carob, mulberry and strawberry tree, have high palatability but also greater regrowth capacity.
Holm oak, cork oak, Portuguese oak and Pyrenean oak fall within an intermediate group in terms of palatability and recovery capacity.
The later groups contain progressively less palatable species, such as rockroses, rosemary, Phlomis purpurea, mastic and broom.
This classification helps interpret field observations more accurately: the same level of browsing does not have the same meaning for every plant species.
Plants can also act as indicators
When a highly palatable species is browsed, this does not necessarily mean that overgrazing is occurring, because livestock will naturally select it.
However, when less palatable species begin to show heavy browsing, the interpretation changes.
The protocol states that when species with a high capacity to regrow are heavily browsed, this may indicate high grazing pressure that threatens tree regeneration.
The warning becomes even clearer when Mediterranean trees such as holm oak or cork oak are visibly affected. If these species show significant consumption, regeneration may be at risk and grazing intensity may be excessive.
From field observation to a score
To make monitoring more objective, the document proposes recording the level of consumption or damage for each species.
The scale ranges from:
- 0: no consumption
- 1: slight consumption
- 2: low consumption
- 3: medium consumption
- 4: high consumption
- 5: total consumption
This assessment is then combined with the palatability and regrowth class of each plant.
In this way, a simple field observation can be transformed into a practical monitoring tool.
The key reference: remain below 5
The protocol proposes a final score for interpreting conservation status and the natural regeneration capacity of shrub vegetation.
According to the document, to ensure regeneration of the dehesa and shrub pastures, the score should remain below 5.
This does not mean that livestock should not browse.
Highly palatable species may show relatively high use. However, in the case of Quercus species such as holm oak and cork oak, consumption should remain at intermediate levels, with some individuals showing bites but without reaching total defoliation.
Less palatable species should show very few signs of browsing.
Measuring once is not enough
A single assessment provides information about one particular moment. The real value of the method appears when monitoring is repeated periodically.
LIFE ScrubsNet proposes carrying out these assessments over several years in selected, representative patches of vegetation. This makes it possible to detect trends and adapt livestock management according to the objectives of the holding.
If browsing on young holm oaks, cork oaks or less palatable species progressively increases, it may be necessary to review:
- stocking rates;
- paddock occupation periods;
- recovery periods;
- the grazing calendar;
- or even the livestock species and breeds used.
Each holding needs its own interpretation
The protocol also points out that palatability is not completely fixed.
It may vary depending on livestock species, breed and even the individual herd or flock, as well as on the availability of herbaceous pasture and the amount and type of supplementary feed or forage provided.
For this reason, the assessment should mainly be used to compare changes within the same holding, rather than as an identical rule for every farm.
Observe, measure and adapt
Measuring browsing makes it possible to move from a general impression to management based on observable indicators.
The aim is not to prevent livestock from using scrub, but to ensure that this use remains within levels compatible with vegetation recovery.
The LIFE ScrubsNet message is clear: observing which species are being consumed, measuring the level of damage and repeating the assessment over time makes it possible to adapt grazing before regeneration is compromised.
Measure to manage better: a practical tool for making livestock farming, scrub and dehesa regeneration compatible.
The LIFE ScrubsNet project is co-funded by the European Union through the LIFE programme, LIFE20 NAT/ES/000978.