Namibia’s high temperatures pose a growing threat to livestock, crops and soil health, prompting calls for farmers 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 made agricultural production challenging, while extreme heat could further reduce livestock and crop productivity and threaten their survival.

“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,

Heat stress

Ngaruka said cattle, sheep and goats naturally adjusted their behaviour to avoid excessive heat, tending to graze or 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.

Normal body temperatures for cattle, sheep and goats are approximately 38.5°C, 39°C and 39.5°C respectively. When temperatures rise beyond their normal range, animals’ physiological functions can be disrupted and, in severe cases, the effects can become life-threatening.

Digestion also generates heat, meaning animals produce additional internal heat as they process 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,” Ngaruka said.

Animals may respond by reducing their movement and feed intake, affecting their nutritional status, health and productivity.

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

Heat stress can also impair reproduction in both male and female livestock. Ngaruka said high temperatures could disrupt reproductive processes and suppress the release of hormones such as oestrogen and progesterone.

This can affect egg-cell development, the oestrus cycle, conception, embryo development and foetal growth.

In males, high temperatures can interfere with sperm production and may cause temporary infertility.

Shade, water critical

Ngaruka said farmers should limit 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 generally require more of it 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 also advised farmers to adjust the timing of livestock handling and other activities to avoid the hottest parts of the day.

Transporting animals during cooler periods, ensuring adequate shade and ventilation, and scheduling procedures such as vaccination and branding for cooler hours can help reduce heat stress.

Soil and plants at risk

The effects of extreme heat extend beyond livestock. Ngaruka said high temperatures accelerated moisture loss from the 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 dry out the soil and damage microorganisms, organic matter, seeds and plants.

Soil type also influences how quickly the ground heats up and how much moisture it retains. “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 was particularly vulnerable to heat and moisture loss, making overgrazing and excessive land clearing a concern.

Farmers should maintain soil cover by retaining plant litter, applying mulch and preserving dense grass cover where conditions allow, he advised.

Rising water demands

High temperatures increase plants’ water requirements while accelerating 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,” Ngaruka said.

Shallow-rooted plants, including grasses and forbs, are particularly vulnerable to moisture stress. High temperatures and inadequate soil moisture can also inhibit 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,” he said.

Ngaruka said farmers could reduce heat-related losses by planting drought-resistant crop varieties, using drip irrigation and shade netting, and applying mulch and compost to improve soil structure and water retention.

He also urged farmers to strengthen water harvesting and storage measures and use available 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.