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Effects of climate change on owls in South Africa

Owl's House is concerned about how our environment will affect owls in southern Africa. After doing some research we found that the owl - like many other bird species - faces a variety of challenges to maintain its current numbers. These birds of prey play vitally important roles in the preservation of our ecosystems and biodiversity. The high and intermediate conservation priority owl species currently include the African Grass Owl Tyto capensis, the Marsh Owl Asio capensis and the Cape Eagle-Owl Bubo capensis.

Some of the threats to owl populations include:

1. Habitat loss

According to Cape Nature the loss and degradation of habitat continues to be the biggest threat to avian biodiversity in the country. One of the driving forces behind this threat is the escalating human population growth and its associated impacts on the transformation of critical habitat. Important bird habitat such as indigenous forests has been degraded through logging, resulting in a loss or decline of species. These areas have been placed under the management of the South African National Parks, providing the forests and their inhabitants with better statutory protection. As a developing country, South Africa requires sustainable development to improve its economic growth. The regulated Environmental Impact Assessment (EIA) process aims to either prevent development within sensitive areas or mitigate those aspects of development that would seriously impact on the environment.

2. Powerlines

Powerlines pose a serious threat to birds either through birds colliding with the conductors or through electrocution, while landing, perching or taking off from these structures. Eskom is fully aware of the impact that their structures have on South Africa's birdlife and have formed a partnership with the Endangered Wildlife Trust (EWT) to monitor the problem and to develop and improve mitigation measures to reduce bird mortalities. A number of Eskom powerlines in the Western Cape are ending their lifespan and are being refurbished and re-routed around sensitive areas. The erection of powerlines above 33kV is a listed activity in terms of the environmental impact assessment regulations.

3. Roadside bird mortality

With the increase in the number of fast-moving vehicles and the simultaneous development of road building technology, roadside bird mortality has become an increasingly important environmental issue. 554 owls of four species, namely Marsh Owls, the Red Data listed Grass Owl, Barn Owl and the Spotted Eagle Owl were collected on the stretches of the R550 and N17 roads in the rural areas between Springs and Devon in the East Rand of Gauteng Province during the period between October 2001 and September 2003.

It was found that higher traffic speeds definitely having an increasingly detrimental effect on the owl mortalities. Weather conditions also play a role in mortality counts, with the mortalities being significantly negatively correlated to rainfall. Gravel roads had very low incidences of owl mortalities with the highest mortalities recorded along tarmac roads that are bordered by open grasslands or cattle grazing paddocks. Another factor influencing the road mortalities of the owls is grain that is spilled on the road during transport. This initially seemed to be the major factor in attracting granivorous rodents to the roads, and in turn, attracting the owls to prey on them.

4. Climate change

The African climate has always been changing, but the problem with current climate change is thresholds, speed and compound effects. Energy pollution is making the air hotter and richer in CO2 than at any other time in human history - creating 'non-analogue conditions'. Statistical evidence suggests that South Africa has been getting hotter over the past four decades, with average yearly temperatures increasing by 0.13.C per decade between 1960 and 2003.

There has also been an increase in the number of warmer days and a decrease in the number of cooler ones. Recent studies for the 'Country Studies Project' predict that climate change will cause mean temperature increases in South Africa in the range of between 1.C and 3.C by the mid 21st century, with the highest increases in the most arid parts of the country. A broad reduction of rainfall in the range 5% - 10% has been predicted for the summer rainfall region. This is likely to be accompanied by an increased incidence of both drought and floods, with prolonged dry spells being followed by intense storms.

A marginal increase in early winter rainfall is predicted for the winter rainfall region of the country. According to the Climate Systems Analysis Group at the University of Cape Town (UCT), depending on how much fossil fuel was burnt world-wide, up to 45 mm less rain in the Western Cape in July 2050 compared to now can be expected. Up to 50 mm more rain could fall in KwaZulu-Natal in December 2050. A rise in sea level is also predicted - perhaps by as much as 0.9m by 2100.

The rate of current climate change is abrupt and beyond many species' ability to adapt. Changes in patterns of temperature and rainfall and the intensity and frequency of severe weather events, storms, floods, droughts and wildfires, will challenge our biodiversity. These effects threaten substantial damage to or complete loss of some unique ecosystems, and extinction of some critically endangered species. It has been projected that approximately 20 to 30% of plant and animal species assessed so far would likely be at an increasingly high risk of extinction should global mean temperatures exceed a warming of 2 to 3.C above pre-industrial temperature levels.

Birds are certainly among the most visible and evocative to us as a society, and are thus an important window into the broader changes in ecosystems. Just as the mining industry once used canaries to indicate air quality in mine shafts, the status and trends of bird populations are powerful indicators of the health of our planet.

Two organizations, the Endangered Wildlife Trust's Birds of Prey Working Group, and the Western Cape Raptor Research Programme based at the Percy FitzPatrick Institute of African Ornithology at UCT, are monitoring and conducting research on vultures, migratory kestrels, harriers, falcons, eagles and owls to determine our environmental health. Areas with healthy and diverse ecosystems should form an important buffer from the most severe impacts of climate change. 'It potentially has an impact on more localised species that require specific habitat conditions which may be affected through climate change. From an available resource perspective, we are more pressed to currently focus on the more direct anthropogenic threats owls face that has a far more substantial impact on populations of a range of species in the region,' Andre Botha, Manager of the Birds of Prey programme at the Environmental Wildlife Trust said.

According to SABAP2 at UCT's Animal Demography Unit, climate change will impact owls in five ways:

Distribution: A species can only move if its food moves. If the climate gets warmer all the biological components on which it depends ought to move polewards.
Timing of migration: One of the realities of climate change is that the spring in Eurasia begins earlier each year and consequently the period in which food is abundant. Breeding is timed so that maximum demand by growing chicks coincides with the food flush.

Abundance: As climate changes across the range of a species, that bird is likely to become more common in some parts of its range and rarer or disappear in other parts.
Composition of bird communities will change.
Changes in size and shape: Species that stay in the same place as the climate changes, have to adapt - some have become smaller as the planet has warmed.

'This is the first evidence of Climate Change having such an effect on the Animal Kingdom'
by Victoria Gill, BBC News

Many African Important Bird Areas (IBAs) are predicted to experience a major loss of species as bird distributions change in response to a changing climate - 62% of bird species are predicted to lose climatically suitable space. The study reveals that it is likely that species will move out of the current locations of reserve networks and designated conservation areas or face local extinction. 'There are numerous species whose ranges are changing markedly, and indeed some of these seem difficult to ascribe to any other cause than climate change,' said Dr Phoebe Barnard of the SANBI Climate Change and BioAdaptation Division.

The north-western and central regions of South Africa are predicted to lose all climatically suitable space for all species modelled. However, no species are predicted to go 'extinct', meaning that there is at least some suitable climatic space remaining under climate change for all species assessed.

'Some species such as the Spotted Eagle Owl and Barn Owl have proven to be quite adaptive and occur in a wide range of habitat, including urban areas and it may be that the impacts of climate change would not be substantial on these species as a whole. Habitat specialists such as the African Grass Owl and Pel's Fishing Owl may however be more affected due to changing rainfall regimes and changes in the growth season of vegetation as a result of this,' Botha said.

The impacts of climate change on owls serve as reaffirmation that drastic decrease in global carbon emissions is necessary to safeguard species. Failing that, we need protected area management and IBA design to incorporate climate change, because the geographical areas that are currently important for conservation are very likely to change.

This trend is disconcerting, as it means there are fewer opportunities for conservation as the bioclimatically suitable space for many species is condensed into an ever smaller area.

South Africa, the 3rd most biodiverse country in the world, is itself a contributor to the global climate change problem. In 1990, South Africa was responsible for about 1.2% of the total global warming effect which placed it within the top ten contributing countries in the world. The carbon dioxide equivalent emission rate per person in South Africa (about 10 tons of CO2 per person per year) is above the global average (7 tons pppy) - although this is still considerably below that of developed countries such as the United States (20 tons pppy - 1991). The burning of fossil fuels in South Africa is the primary source of this carbon dioxide.

For the sake of our owls, we each need to reduce our carbon footprint. We also need to assist these birds of prey to adapt to climate change. 'Unless we reduce our current impact on many of their habitats, this will be a difficult thing to achieve,' Botha said.

Helping preserve their habitats through methods such as erecting owl posts, is a step in the right direction. It's easy to do it yourself and you can order your Owl House in-a-box here.

by Willemien Calitz
Environmental Journalist

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Environmental Journalist.
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By Willemien Calitz


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