Destocking, Boreholes and Salinity in a Drought-Stressed Conservancy
The !Aris communal conservancy covers 14,000 hectares of semi-desert and currently carries 2,300 cattle and 3,000 goats. Rangeland officers estimate a safe long-term stocking rate of one large stock unit (LSU) per 12 hectares, counting six goats as one LSU. Last season's rainfall was 180 mm against a long-term mean of 320 mm. The conservancy's three boreholes supply households, livestock and a small guest farm. Pump tests show the main borehole has fallen from 2.5 to 1.2 litres per second and its salinity has risen from 1,800 to 3,400 mg per litre total dissolved solids. A second water point, 9 km from the village, is expected to fail within two months, which would force animals to walk to the main borehole. Drilling a replacement would cost N$850,000 and the local success rate at that depth is about 40%. The committee meets next week; the next rains are eight months away, and the guest farm has two bookings already paid for and uses about 4,000 litres a day.
1. Calculate the conservancy's carrying capacity and explain which animals the committee should sell and in what order.
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Calculation: 14,000 ha ÷ 12 ha per LSU = 1,167 LSU as the safe long-term herd. Current herd in LSU: cattle 2,300 × 1 = 2,300 LSU; goats 3,000 ÷ 6 = 500 LSU; total 2,800 LSU. Overstocking = (2,800 − 1,167) ÷ 1,167 ≈ 140% above capacity - roughly 2.4 times the safe figure. To reach capacity the conservancy must remove about 1,633 LSU, i.e. 58% of its herd.
Order of sale - reasons, not just numbers:
- Steers, old oxen and cull cows first. They contribute no future calves and their condition will fall fastest on short grazing; selling early, before they lose value, is better than selling weak animals late.
- Dry and barren females next, then aged breeding cows, keeping the youngest productive cows as the herd's core.
- Goats last, and only partly. Goats browse shrubs that cattle cannot use, so 3,000 goats on this land are not equivalent damage to 500 LSU of cattle; each goat sold also realises a small amount of cash only.
- Do not sell all breeding females, or recovery after the rains is delayed by years.
A defensible target is to cut to roughly 1,600–1,800 LSU now - above the theoretical 1,167, because the calculation assumes an average year and the range is already degraded - then destock further if the next rains fail again. Numbers must be agreed in writing with the guest farm and the traditional authority, because voluntary cuts rarely hold.
2. Evaluate the new borehole proposal against the other options and explain what the rising salinity means for decisions the committee must make now.
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Borehole economics: N$850,000 with a 40% success chance means the expected cost per successful hole is about N$2.1 million, and there is a 60% chance of spending the money and gaining nothing. Even a successful hole may hit the same saline water at depth. It also does not reduce the stocking problem: extra water lets more animals survive, which increases grazing pressure on land already damaged by a 180 mm season.
Other options: buying fodder is short-term and expensive at drought prices; leasing grazing elsewhere preserves the herd only if transport cost per head is below the sale value; splitting the herd between the two working water points spreads risk but the second point fails in two months anyway. The cheapest immediate saving is to cut the guest farm's demand - 4,000 litres a day for two bookings - by installing low-flow fittings, a tank and a signed water-use clause, so household supply is protected.
Salinity: 3,400 mg/L TDS is far above the ~1,000 mg/L that cattle prefer and is enough to reduce feed intake and weight gain; sheep and goats tolerate it better than cattle, and young animals worst of all. It also corrodes pumps and plumbing and is unpleasant for people. So the committee should treat the main borehole as a livestock-only source, protect a separate potable source for households, test salinity monthly, and set a threshold (say 4,000 mg/L) at which cattle are removed. Priority is destocking plus demand management; the borehole is a gamble, not a solution.