Climate change and livestock : Impacts and mitigation
- Part 1 -

P Mayengbam / TC Tolenkhomba *

Introduction

The Earth’s climate has changed throughout history. Just in the last 650,000 years there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives.

The evidences for rapid climate change include global temperature rise, warming oceans, shrinking ice sheets, glacial retreat, decreased snow cover, sea level rise, declining arctic sea ice, ocean acidification, etc. (http://climate.nasa.gov/evidence/). Taken as a whole, the range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time.

The future effects of climate change are predicted to continue the climate change through this century and beyond, continuous rise of temperature, changes in precipitation, more droughts and heat waves, stronger and intense hurricanes, rise of sea level 1-4 feet by 2100 and arctic likely to become ice-free (https://climate.nasa.gov/effects/).

Climate change scenario in India

Annual mean temperature of the country as a whole has risen to 0.510C over the period 1901-2005 (Rupa Kumar et al., 2006) and the rise was mainly due to rise in maximum temperature. Since 1990, minimum temperature is steadily rising and rate of its rise is slightly more than that of maximum temperature.

July rainfall has significantly decreased for most of the parts of the central and peninsular India but has increased significantly in the North Eastern parts of the country. August rainfall has increased significantly for the sub divisions Konkan and Goa, Marath-wada, Madhya Pradesh, Maharashtra, Vidarbha, West MP, Telengana and West UP.

September rainfall has shown significantly decreasing trend for sub divisions Vidarbha, Marath-wada and Telengana and increasing trend (95%) for the subdivision Sub Hima-layan Gangetic West Bengal.

The summer monsoon accounts for 70-80% of the annual rainfall over major part of India. Due to large variability in the monsoon pattern, India experiences drought or floods in certain agro-climatic zones between June-September. And the droughts are due to failure of rains from southwest monsoon.

Contribution of Livestock to climate Change

The livestock sector I one of the main contributors to Green House Gases (GHG) emission in India. Enteric CH4 emission of 160.495 million indigenous cattle, 24.68 million crossbred cattle, 97.92 million buffaloes (MAO 2003) has been estimated using Tier 2 methodology of IPCC (Upadhyay et al., 2013). The total CH4 emitted due to enteric fermentation and manure management of 485 million heads of livestock has been worked out at 9.37 Tg/annum for year 2003 (Upadhyay et al., 2007, 2008b).

The major contributors to methane emission were indigenous, crossbred cattle and buffaloes accounting 40%, 8% and 40% respectively. Lactating animals comprising of buffaloes and cattle contributed 3.42 Tg with a major share of 2.04 Tg from lactating buffaloes. Draught animals’ contribution to warming is significant the they emit about 1.2 Tg CH4/annum (Upadhyay et al., 2008a).

However, for pigs and chickens the largest source of emissions is due to feed production (between 25% and 27%), which includes fertilizer production, machinery use, and feed transportation. Enteric fermentation from pigs is much lower than in ruminants because their digestive process does not produce as much methane as a by-product (Gerber et al., 2013).

An assessment of the current and projected trends of GHG emission from India and some selected countries indicates that though Indian emissions grew at the rate of 4% per annum during 1990 and 2000 and are projected to grow further to meet the national developmental needs, the absolute level of GHG emissions in 2020 will be below 5% of global emissions and per capita emissions in 2020 will be low compared to most of the developed countries as well as the global average emissions (Sharma et. Al., 2006).

The emissions from livestock sector are also low per head considering multiutility of Indian livestock for milk, meat and work, but sizable number of nondescript cattle maintained primarily for draught need to be reduced in present context of climate change due to CH4 emission per head of livestock (Upadhyay et al., 2013).

Climate Change and Increase in Thermal Stress

All animals have a thermal comfort zone, which is a range of ambient environmental temperatures that are beneficial to physiological functions (FAO, 1986). During the day, livestock keep a body temperature within a range of ± 0.5 C (Henry et al., 2012). When temperature increases more than the upper critical temperature of the range (varies by species type), the animals begin to suffer heat stress (FAO, 1986). Heat stress on livestock is dependent on temperature, humidity, species, genetic potential, life stage, and nutritional status.

Livestock in higher latitudes will be more affected by the increase of temperatures than livestock located in lower latitudes, because livestock in lower latitudes are usually better adapted to high temperatures and droughts (Thornton et al., 2009). Confined livestock production systems that have more control over climate exposure will be less affected by climate change (Rotter and van de Geijn, 1999).

Ambient temperature higher than 250C with relative humidity greater than 50% has a negative impact on animal productivity. Different livestock species and breeds have different tolerance levels for temperature and humidity.

Temperature Humidity Index (THI) has been used to relate animal stress. Animals are comfortable at THI between 65 and 72, under stress from 72 to 78 and under severe stress above 80. THI levels during different parts of the year in India indicate predominance of indigenous or non-descript animals in high THI zones due to their better adaptive capacity and ability to cop up with feed scarcity/harsh environmental conditions.

Heat stress decreases forage intake, milk production, the efficiency of feed conversion, and performance (Haun, 1997; McDowell, 1968; Wyman et a., 1962). Warm and humid conditions cause heat stress, which affects behaviour and metabolic variations on livestock or even mortality.

Heat stress impacts on livestock can be categorized into physiological functions, feed nutrient utilization, feed nutrient utilization and feed intake, milk production, reproduction, livestock health, and efficiency of production system. The following presents these in more detail.


To be continued....