Heatwaves threaten livestock, crops and soil health

Namibia’s high temperatures increasingly threaten livestock, crops, and soil health, and farmers are urged to prepare for heat stress by improving water management, providing shade, and protecting soil cover.

Technical adviser for Livestock and Rangeland Management Erastus Ngaruka said Namibia’s predominantly dry conditions already make agricultural production challenging, and extreme heat could further reduce the productivity and survival of livestock and plants.

“Namibia is largely a dry country, which compromises optimal agricultural production. The imminent heatwaves will exacerbate these challenges,” Ngaruka said.

He said livestock production was particularly vulnerable because much of Namibia’s farming relies on extensive grazing systems, while crop production is largely dependent on rainfall.

Heat stress

Ngaruka said cattle, sheep and goats naturally adjust their behaviour to avoid excessive heat, with animals tending to forage during cooler periods.

“Ruminant animals such as cattle, goats and sheep, under normal circumstances, prefer to graze or forage during cooler hours of the day, such as early morning, late afternoon or evening, to avoid heat stress,” he said.

The normal body temperatures of cattle, sheep and goats are about 38.5°C, 39°C and 39.5°C respectively. When temperatures rise beyond their normal range, their physiological functioning can be affected and, in extreme cases, become life-threatening.

Ngaruka said digestion also generates heat, meaning animals produce additional internal heat while processing feed. “Grazing during the hot hours exposes animals to excessive heat from both direct sunlight and the internal digestive processes, increasing the risk of heat stress,” he said.

Animals may respond by reducing movement and feed intake, which can affect their nutrition, health and productivity.

“The consequences can include poor growth, declining body condition, reduced milk production and poor reproductive performance,” Ngaruka said.

Heat stress can also affect livestock reproduction, with high temperatures disrupting reproductive processes in both male and female animals.

Ngaruka said heat stress could suppress the release of reproductive hormones such as oestrogen and progesterone, affecting processes including egg-cell development, the oestrus cycle, conception, embryo development and foetal growth.

In males, high temperatures can affect sperm production and may result in temporary infertility.

Shade and water critical

Ngaruka said farmers should reduce livestock exposure to extreme heat by providing shade, particularly in kraals where young animals may spend long periods. “It is critical to provide shade in the kraals by having trees or using shade nets or other appropriate shading materials,” he said.

Water is equally important, as livestock require more water as temperatures rise.

“In hot environments or when animals forage during the hot hours of the day, the water demand or intake increases. Thus, animals should have daily access to clean, cool and sufficient water,” Ngaruka said.

He said farmers should also adjust the timing of livestock activities. Animals should be transported during cooler periods, with sufficient shade and ventilation, while activities such as vaccination and branding should be carried out during cooler hours.

Soil, plants at risk

The effects of extreme heat extend beyond livestock. Ngaruka said higher temperatures accelerate moisture loss from soil through evaporation and from plants through transpiration. “Heatwaves or high temperatures that are expected with the El Niño event will be detrimental to soils, plants, livestock and livelihoods,” he said.

Extreme soil temperatures can contribute to drying and damage soil microorganisms, organic matter, seeds and plants.

Soil type also affects how quickly soil heats up and how much moisture it can retain.

“Sandy soils have lower water retention capacity and heat up much more than clay soils, which have a higher water retention capacity,” Ngaruka said.

He warned that bare soil is particularly vulnerable to heat and moisture loss, making overgrazing and excessive land clearing a concern.

Ngaruka advised farmers to maintain soil cover by retaining plant litter, applying mulch and maintaining dense grass cover where possible.

Water demands

High temperatures increase both plant water demand and evaporation, placing additional pressure on crops and grazing vegetation.

“The higher the environmental temperature, the higher the water demand. On the other hand, the higher the environmental temperature, the higher the rate of evaporation,” he said.

Shallow-rooted plants such as grasses and forbs are particularly vulnerable, with heat stress potentially inhibiting seed germination and grass growth.

“Seed germination or grass growth will be inhibited, ultimately leading to poor rangeland productivity or poor grazing conditions, compromising livestock performance and survival,” Ngaruka said.

Ngaruka said farmers could reduce heat-related losses through measures such as drought-resistant crop varieties, drip irrigation, shade netting, mulch and compost to improve soil structure and water retention.

He also urged farmers to improve water harvesting and storage and use water conservatively.

“Farmers need to prepare in advance to withstand the effects of drought and heat stress by improving water harvesting, storage and conservative use, and improving farm infrastructure to protect livestock and crops from excessive heat exposure,” Ngaruka said.