background essentials

able development goals. This SI policy goal applies also

to research on tropical pastures and forages and is reflect-

When considering livestock production in the tropics and

ed, for example, in the theme of the last International

its impact on the environment, a few issues should be

Grassland Congress (New Delhi, India, November 2015):

highlighted:

Sustainable Use of Grassland Resources for Forage Pro-

 In the scientific and non-scientific communities,

duction, Biodiversity and Environmental Protection.

livestock production, including grazing, is blamed for

Two recent overview analyses of tropical forage-based

severe negative impacts on the environment (e.g.

livestock production systems vis-à-vis the environment and

Steinfeld et al. 2006; Hyner 2015). Livestock production the need for SI concluded that such systems can have a

is estimated to contribute 14.5% of all anthropogenic

positive impact on the environment (Peters et al. 2013; Rao

GHG emissions globally (Gerber et al. 2013).

et al. 2015). In tropical production systems, the term

 The demand for animal products, especially foods derived

‘forages’ refers mostly to grasses, since adoption of legume

from livestock, is expected to increase consid-erably in the

technology in the past has been rather low (Shelton et al.

future, particularly in South, East and Southeast Asia, and

2005). We hypothesize, however, that tropical forage

to a lesser extent in Sub-Saharan Africa, as a consequence

legumes do have the potential to play a particular, positive

of increasing living standards (Rosegrant et al. 2009;

role in addressing environmental concerns.

Robinson and Pozzi 2011).

Therefore, complementing the above-mentioned over-

 In view of physical limitations to expansion of land

views and in order to contribute to the development of

area for agricultural production (both crop and

research strategies, in this paper we analyze the effects of

livestock), future production increases must come

tropical forage legumes (pasture plants for grazing or

mainly from intensification of production systems

fodder plants for cut-and-carry or browsing) on the

(The Montpellier Panel 2013).

environment. For this, we briefly: outline the main anthro-

 Ruminant livestock (e.g. cattle, buffalo, sheep, goats)

pogenic environmental issues; highlight some essentials

play an important role as they convert vegetation,

related to livestock production and the environment; and

which is unsuitable as food for humans, into high-

discuss the key attributes of forage legumes that con-

quality products for human consumption. Nonethe-

tribute to natural resource conservation and environ-

less ruminants are fed grain-based diets (such as in

mental protection with a particular emphasis on

feedlots), and this practice is in direct competition with

adaptation to and mitigation of climate change. We then

humans for that food source (Mottet et al. 2017).

examine the potential of tropical forage legumes to have

 Tropical grazing lands often occupy marginal land that

a positive impact on environmental issues and provide

is unsuitable or only marginally suitable for crop

ecosystem services.

production, because of constraints imposed by soil

Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)

Tropical forage legumes and environment 3

physical and chemical properties, topography

3. Many legumes have a deep-reaching taproot system,

(including slopes and waterlogging) and climatic

providing access to water and nutrients in deeper soil

conditions (Rao et al. 2015). Similarly, some lands are

layers (Rao 1998; Dubeux et al. 2015), which temporarily unsuitable for crop production due to

contributes to improved cycling of both N and P

drought or excess of water, and these areas are

(Thomas 1995; Oberson et al. 2006).

expected to increase in the tropics (Zabel et al. 2014).

4. There is an enormous organismal (taxonomic) and

Here, crop production could benefit from a crop-

genetic diversity in the Leguminosae (or Fabaceae)

forage rotation.

family with almost 20,000 species (Williams 1983;

 As far as research on tropical pastures and forages is

Lewis et al. 2005) in formerly 3, now 6 (LPWG 2017), concerned, the literature provides almost no indication

subfamilies. This includes annuals and peren-nials,

that, in the past, environmental issues have played a

growth forms ranging from herbaceous, prostrate

major role in forage development and utilization.

species (e.g. Arachis pintoi) to vines (e.g. Centrosema

spp.), subshrubs (many Stylosanthes spp.), shrubs (e.g.

Notable exceptions are the concerns expressed by

Cratylia argentea) and trees (e.g. Leucaena spp.).

McIvor et al. (1997; 2005) and Noble et al. (2000).

Such diversity suggests that a very wide range of

production-relevant features, in terms of adaptations to