Data from: Remotely-sensed primary productivity shows that domestic and native herbivores combined are overgrazing Patagonia

1. Carrying capacity is the maximum density of animals an area can sustain
without a deterioration of its resources. Overgrazing degraded Patagonia
grasslands in the past, but sheep stocks decreased in the last three
decades and gave way to a mixed system with cattle, goats and guanacos
(native wild camelids). 2. The objective of this paper was to develop a
method to estimate carrying capacity based on remotely sensed data, and to
assess wild and domestic herbivore numbers to establish if combined
grazing stocks have evolved to a balance with carrying capacity. 3. Net
Primary Productivity (NPP) MOD17/A3 images and Aerial Net Primary
Productivity (ANPP) data of 66 sites were linearly regressed (R2= 0.83,
P<0.01), and the slope 0.236 was used to convert MOD17/A3 NPP to
ANPP. The proportion of ANPP that can be sustainably consumed (Harvest
index) was HI=-5.71+0.72 ANPP0.5. Consumable forage was CF =ANPP.HI and
carrying capacity CC =CF.EAC-1, where EAC is an estimate of annual
consumption: 500, 3200 and 750 kg DM.head-1.year-1 for sheep or goats,
cattle and guanacos, respectively. 4. Regional ANPP±SD (2000-2015) was
758±52 kg DM ha-1.yr-1; HI= 13.7±0.6% and CF= 104±12 kg DM ha-1yr-1
resulting in regional carrying capacity of 14.8±1.6 M sheep or goats,
2.3±0.3 M cattle or 9.9±1.2 M guanacos. 5. Domestic stock was high from
1920 to 1980, but declined thereafter and remained mostly within ±1SD of
carrying capacity in this century. Annual mean provincial stocks and
carrying capacity (2000-2015) correlated well (R²= 0.94, p<0.01)
with a slope close to 1. 6. Guanacos increased from 0.5 M to 2 M between
2000 and 2015, driving linearly combined grazing pressures 36 and 62%
above carrying capacity in southern Patagonia provinces in 2015. 7.
Synthesis and applications: Herbivore de-stocking is necessary to restore
grazing balance in south Patagonia. Guanacos are capable of grazing
low-quality food and maintain production during dry periods, and their
meat and fibre may be incorporated and combined with sheep production.
Management of population of guanacos in mixed grazing systems with
adjusted stocks may prevent further rangeland degradation, farm
abandonment, and loss of ecosystem services of these
rangelands.05-Apr-2019