ecosystem services to and from north american arid ... - Conabio

IV SIMPOSIO INTERNACIONAL DE PASTIZALES
San Luis Potosí, S.L.P. México; 22 al 24 de agosto de 2007
Artículos in extenso
Área temática: Transferencia de Tecnología
activity (Zhu et al., 2005). Hence it is important to understand plant growth dynamics and
utilization to achieve better rangeland conservation.
The good news for extensive grazing producers are that the world beef demand will increase
within the next years (Delgado, 2005) and this demand must be supplied by efficient and less
polluting production systems (Kibblewhite, 2005), due to the fact that residue management
increases costs as well as public pressure on intensive production systems. Cow-calf extensive
systems will continue to be an important source for the beef cattle market (Bowman, 2005).
Grazing animal production, dominant within arid rangelands, will render better results for farmers
with the best rangeland condition; this can be attained through good management and
rangeland improvement practices such as: grazing enterprise efficiency, marketing strategies,
and lower production costs.
Expected changes of land property in Mexico may be a higher source for financial certainty and
support for productive enterprises; however, rain-fed systems primary productivity will
continuously be conditioned by drought and winter temperatures. Despite any resultant, land
property structure or the productive land organization, ecological principles must be observed in
order to attain stable production systems under those constant premises. Hence, it is a pertinent
action to achieve the integration of a solid grazing management scheme as fast as possible in
order to promote that the grazing production systems do not affect the arid rangeland
ecosystems in Mexico, whose stability has been put under risk (Briske, 1993). Rangeland
productivity must become again a well-being generator (economic, educative, cultural, etc.),
producing citizens technically qualified that look and take advantage of opportunities for the rural
family integral development.
RANGELAND AND GRAZING
There are two equitable to the ecosystem grazing models: equilibrium model and dynamic model
(Rowntree et al., 2004). The equilibrium model is based on the principle that vegetation is tied to
long term conditions, mainly rain and physiography, pursuing toward climax conditions,
according to water availability on the long term. The dynamic model is based on the high
variability of rain as vegetation conditioner and hence the rangeland’s grazing carrying capacity.
Optimal carrying capacity allows vegetation to achieve successive stages of climax. Grazers and
vegetation will reach equilibrium through continuous adjustments within a dynamic relation.
Overgrazing will maintain the vegetation under sub-climax conditions, dominated by pioneer
plant species with low dry matter production and palatability. Optimal carrying capacity combines
grazing (with long term data to define it), rest from grazing, livestock rotation, as well as a careful
use of fire. Fixed carrying capacity under grazing will produce regular overgrazing events and
hence, grazing population must be dynamically adjusted. As long as the vegetation recovers
from drought or winter, the carrying capacity may increase. Plant condition determines the
carrying capacity and the water precipitation defines vegetation condition (Rowntree et al.,
2004).
There have been emergency plans to support drought effects in Mexico’s arid rangelands, and
these became eternal and inefficient palliatives, due to the fact that these support the inefficient
herd maintenance and do not reduce grazing pressures for the rangeland within a due time.
Under such circumstances, any normal recurrent drought is considered as extreme
phenomenon, due to the dynamic relation among plant condition and carrying capacity, as well
as the mismanagement of the communal rangeland. Any normal drought becomes an
emergency under the lack of standards. On the other hand, no plans for forage abundance exist.
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