Climate change and variability affect rangeland quality and productivity-how?

Abstract

Climate change is a principal threat to the sustainability of our planet which consists partly of the world’s rangelands. According to numerous studies and reports, the trend at which the global climate is changing is a clear indication that the long term sustainability of global rangelands is uncertain. There is abundant evidence of climate change across the globe. The global average surface temperature is predicted to increase between 1.8°C and 4.0°C by 2100. This will no doubt have adverse and tremendous impact on the quality and productivity of rangelands, which in turn is expected to affect ruminant livestock production since about 70 % of forages fed on by animals are produced from these rangelands. The current climate change is basically as a result of anthropogenic activities leading to a build up of greenhouse gases in the atmosphere. These gases are trapped in the atmosphere and in return increase global surface temperature and alter known climatic patterns globally. This review, therefore, highlights the effect of climate change on rangeland quality and productivity considering how the drivers of climate change impact on the length of the growing period, plant species composition, nutritional value of forages, drought stress in plants, lignification, vegetation flammability and mortality/extinction of range plant and animal species. The review revealed that, climate change will result into the extinction of over one million terrestrial species in the next five decades. The elevation of CO2 levels will increase non-structural carbohydrate content of grasses by 25 % and reduce their nitrogen content by about 8 %. It is also reported that, for every 1 % rise in temperature, there will be 0.4 % rise in Neutral Detergent Fibre decreasing forage intake and digestibility. Rising temperature also results in faster decomposition of soil organic matter. However, minerals will be lost through leaching and erosion if mineral uptake by rangeland plant species is slower than the rate of mineral release into the soil. It is clear that changing climate is having a toll on rangeland quality and productivity, the impact is mixed and difficult to quantify. It is recommended that, much research efforts be put into quantification of climate change impacts on rangelands through modelling and projections simplified for the comprehension of the resource poor livestock farmers particularly in developing countries. Vulnerable rural based livestock farmers should be assisted with adaptation strategies to remain in production. Key words: Composition of plant species, drought stress, nutritional value, plant mortality