Connecting Global Priorities Biodiversity and Human Health

een estimated to be 1–2 μg/kg/day, considerably
higher than the WHO recommendation (0.23 μg/
kg/day) (Passos and Mergler 2008).
The reduction or elimination of Hg use in
ASGM has been receiving widespread attention
(Veiga 2014). Less damaging options include
amalgamating a gold concentrate rather than the
whole ore and using “mercury-free artisanal gold”,
in which gold is isolated by centrifuges and the
gangue materials magnetically removed (Drace
et al. 2012). Awareness and education about Hg
poisoning in ASGM communities is also essential
to ensuring adherence to such changes in ASGM
technology.
4. Impacts of agriculture on water
ecosystems and human health
Unsustainable agricultural practices have
significant impacts on human health, and water
pollution from fertilizers, pesticides and herbicides
remains a serious problem (see the chapter on
agricultural biodiversity and food security in
this volume). Better use of ecosystem services,
underpinned by biodiversity, in agricultural
production systems provides considerable
opportunities to reverse these impacts on health
while simultaneously improving food security.
Agriculture accounts for about 70% of global
water use, and physical water scarcity is already a
problem for more than 1.6 billion people (IWMI
2007). It is increasingly recognized that the
management of land and water are inextricably
linked (e.g. DEFRA 2004). In England, for
example, up to 75% of sediment loading in rivers
can be attributed to agriculture, while 60% of
nitrate pollution and 25% of phosphates in surface
waters originates from agriculture (DEFRA 2007).
Agricultural practices can also contribute to the
spread of water-related and waterborne disease.
For example, significant E. coli loads have been
found in run-off from land grazed by cattle and
treated with livestock wastes (Oliver et al. 2005),
all of which impact the quality of water for human
consumption and use.
Natural vegetation cover in buffers along rivers is
critical to the regulation of water flow, retention of
nutrients, and capture of pollutants and sediments
across landscapes (reviewed in Osborne and
Kovacic 1993). The removal of trees and natural
habitats in landscapes affects soil directly, as well
as the quantity and quality of water draining
from agricultural systems. Riparian buffers of
non-crop vegetation are widely recommended as
a tool for removing non-point source pollutants,
particularly nutrients (nitrates, phosphorus,
potassium) from agricultural areas, especially
those carried by surface run-off (Lee et al. 2003;
Brüsch and Nilsson 1993; Daniel and Gilliam
1996; Glandon et al. 1981; Nakamura et al. 2001).
In field studies, even buffers of switchgrass along
fields removed 95% of the sediment, 80% of the
total nitrogen (N), 62% of the nitrate nitrogen
(NO 3 -N), 78% of the total phosphorus (P), and
58% of the phosphate phosphorus (PO 4 -P). If the
buffer included woody species, it removed 97%
of the sediment, 94% of the total N, 85% of the
NO 3 -N, 91% of the total P, and 80% of the PO 4 -P
in the run-off (Lee et al. 2003).
Nutrient run-off from agricultural sources into
waterways has been blamed for the production of
hypoxia, popularly termed (aquatic) “dead zones”
(Diaz 2001). These destroy local fisheries in many
coastal areas, which communities rely on for the
intake of protein and other nutrients. Dead zones
have now been reported in more than 400 systems,
affecting a total area of more than 245 000
square kilometres (Diaz and Rosenburg 2008;
see Figure 1). These are concentrated along the
eastern seaboard of North America, and European
and Japanese coastlines, where human ecological
footprints and agriculture intensities are highest
(Diaz and Rosenburg 2008, see Figure 1).
Agricultural practice and its demand for water
have reduced both the amount and quality of
drinking water available for human consumption.
At the same time, lack of irrigation in many lowincome
countries is a leading cause of poor crop
production and yield gaps (Lobell et al. 2009). By
2002, irrigated agricultural land comprised less
than one fifth of all cropped area but produced
40–45% of the world’s food (Döll and Siebert
54 Connecting Global Priorities: Biodiversity and Human Health