We and our relation with the food chain and the environment

Although we like to believe the we humans are the center of the universe, in fact we are not. We are among the last organisms that appeared on earth – long after bacteria, protists, invertebrates, fishes and reptilians – and we totally depend on many other forms of life on this planet for our survival.

We are just one element – perhaps a special and fascinating one – of a complex integrated ecosystem that includes all the other components on this planet, living and not living. Human life would not exist if all these other components of the biosphere were not here, or if we fail to respect a delicate equilibrium.

Equilibrium means balance. Living entities (humans, animals, plants, bacteria) and non-living things (like sunlight and water) need to stay in equilibrium for their survival and reproduction. Too many or too few of a given species – including us – can cause a population to suffer or even crash. We all know that some species have gone extincted, in the past as well as more recently.

The food chain begins with organisms known as primary producers, that are capable to use radiation from the sun as an energy source, like plants and some microorganisms. It ends with apex predators (like lions), detritivores (like earthworms) and decomposers (such as bacteria). Basically, the food chain shows how organisms are related to each other based on what food source they consume. Humans are on the top of the food chain, when they eat meat products obtained from animals, which consumed smaller animals and plants, etc. However, in case of vegetarians, who are herbivores, humans can be considered as primary consumers.

If we damage or interrupt one component, inevitably we alter a delicate equilibrium, and this affects us in many ways (for example the DeepWater Horizon in the Caribbeans, Chernobyl in Russia, the methane release due to thawing permafrost soil in Siberia).

Chemicals enter the food chain in many ways. We can get exposed from fruits and vegetables, directly or indirectly, if these are treated with various chemicals or if we dispose of wastes improperly. Fishes eat plancton, bigger fishes eat smaller fishes, then we eat them and we get exposed.

We have to face it: chemical analyses tell us with no doubt several chemicals of non-natural origin are present in food and drinks, in our body fluids and in the environment. Some clearly derive from plastics, packaging and FCM, but the list of chemicals also includes medicines and antibiotics, for humans or for veterinarian use.

Although this is not our main subject, chemicals that end up in the environment alter the soil microbiota, affect the growth and seasonal reproduction, modify or interrupt that delicate equilibrium and in the end will return to humans in many negative ways.

The environment in part can tolerate or destroy these chemicals, but this requires time. In the meantime, before being naturally destroyed, chemicals could heavily disturb the soil microbiota and affect wildlife. A similar natural history can be told about microplastics (see the interview with Dr. Starowicz).

Subtle changes can have subtle – but not less important – consequences. For example, if we give hormones to cows, when we eat meet or drink milk we may receive traces of those hormones. If we give antibiotics to chickens, then we get traces of those antibiotics. If we dump chemicals in rivers, or plastic in the oceans, these materials travel up the food chain and will come back to us. Also consider that some chemicals do not biodegrade, or they take a very long time, thus their effects may be long-lasting.

Bioaccumulation

Upon passaging through the food chain, some chemicals, instead of being diluted, tend to accumulate. For example, do you recall about the pollution of mercury in ocean waters ? Researchers found that mercury was uptaken from fishes and then people who ate contaminated fishes faced serious health problems.

Another interesting story is about the antler tissue of the red deer, a wild animal. This tissue is an excellent reservoir of polluting substances and by analysing this tissue we can have a clear picture of environmental pollution that has taken place many years ago, has accumulated and perhpas is still occurring.

In the previous activities, you have seen the importance of the type of chemical, concentration and tolerated dose for our health and safety. Accelerated urbanization and industrial development in recent years increased an occurrence of micropollutants in the environment. The harmful compound come from pharmaceuticals (antibiotics, drugs), steroid and hormones used in farming, industrial additives, plant protection products or insecticides. Recent studies are focused on wildlife forest animals and here we touch on this issues with three examples and some research findings.

Don’t miss the see also materials that contains three important examples on the topic.

see the interview