Biodiversity loss continues at unprecedented rates; 1000 times faster than it should without anthropogenic activities (Slingenberg et al., 2009). Thus, humanity is causing the sixth mass extinction, the only one caused by humans (Barnosky et al., 2011). In my previous article on these pages, I outlined four main human activities that are causing this high loss of biological diversity: habitat loss and or fragmentation; resource overexploitation; invasive alien species; and climate change. This article will focus on the first. Habitat loss or fragmentation has been considered to be the driving force of species extinction worldwide (Pimm and Raven, 2000). Globally, agriculture is the biggest cause of habitat destruction. Distressingly, one-third of all food produced for human consumption is wasted, according to the Food Agriculture Organisation. Saving food can be a small deed with a big impact!

The principal concern of all species is to feed themselves and to avoid being eaten so that they can pass on their genes or reproduce. Habitat (where an organism lives naturally) is lost when it can no longer provide its inhabitants with food, shelter, and convenient mates. It is fragmented when divided into many small isolated patches (Cheptou et al., 2016) that, most of the times, cannot sustain the minimum viable populations (Flatcher et al., 2011;). When a small population is spatially isolated in a small habitat, relative individuals (like siblings) have no choice but to breed between themselves. As a result, their offspring have less Darwinian fitness (Sinervo et al., 2000; Galliard et al., 2004). This is known as inbreeding depression (Freeland, 2005). Because their genetic diversity is too low to cope with change, inbreeding exposes these populations to extinction vortex (Fagan and Holmes, 2006).

Sometimes the matrix (the space between patches) is so harsh or wide that it makes it too hard for individuals to cross.Think about a small frog carrying a tadpole or her back crossing an eight-metre wide road in Nyungwe National Park. It is like an old woman climbing Kigali City Tower with a baby in her hands. Hard and risky! Clearly, habitat loss and fragmentation have strong negative impacts on species richness (Laurance et al., 2002), population abundance, genetic diversity (Aguilar et al, 2008), trophic food chains, foraging success, dispersal, and species interactions (Jackson and Fahrig, 2013).

Though there are other factors including, mining, logging, infrastructural development, and urban expansions, it has been clarified that agriculture is the major cause of habitat loss and fragmentation (Sodhi & Ehrlich, 2010). Savannahs, wetlands and aquatic systems were converted and polluted, but forests have been hit hardest. Twenty-five nations have virtually lost their forest cover, and another 29 have lost 90% of their forests (MA, 2005). Tropical forests are disappearing at up to 130, 000 km2 a year; 50 football fields per minute (Sodhi & Ehrlich, 2010). However, 17 of the 25 biodiversity hotspots (areas with 0.5% of all plant species, high endemism and which have lost 70% of their vegetation, each) are found in tropical humid forests (Pimm and Raven, 2000). These hotspots cover 1.4% of the global surface area, but they are home to 44 per cent of all plant species and 35 per cent of all vertebrate species.

Sadly, one-third of all food produced for human consumption is wasted, according to FAO. Food wastage takes the third place as a top emitter of CO2, after the US and China. The economic value of the food wastage is distressing; USD 750 billion (FAO, 2013), the GDP of Switzerland of 2015 or an annual budget of Rwanda for nearly 31 years. This wasted food is enough for 2.5 billion more people. Yet, almost a billion people are going hungry worldwide.

The more food wastage the more natural ecosystems are destroyed, the worse global climate change grows, the more soil we lose to erosion, the more money our countries spend on fertilisers, antibiotics and pesticides, all with deadly collateral consequences. Fertilisers, antibiotics and pesticides are produced by a handful of multinationals. By wasting food, the affluence of the few and the misery of the many are encouraged. It is unacceptable, it is not sustainable. Ecosystems affected by human food production are critical to our survival. We are part of the web we are poking holes into.

There are people who confound wasting food with being affluent. In his book, My Autobiography (2013), Sir Alex Ferguson said: "Rockefeller’s hard work instilled a frugal nature in him. He didn’t waste. There is a touch of that in me. Even today, if my grandchildren leave something on the plate, I take it. I was the same with my three sons – DON’T LEAVE ANYTHING ON YOUR PLATE – was a mantra.” Let us be responsible consumers!

The writer is pursuing an International Master in Applied Ecology (IMAE) in France (Université de Poitiers), Ecuador (Universidad San Francisco de Quito) and Portugal (University of Coimbra).