Humans and Animal Migration: A Complex and Interwoven Issue

Insights into the effects of human activity on animal migration

By Amanda Winstead

Of all the animals, modern humans have a unique ability to change our environment to suit our own needs. From street lamps to hydroelectric dams, we find ways to alter the very essence of the places we call “home”, and can settle permanently on six of the seven continents. In fact, 50-70% of the earth’s surface is currently being altered by human activity.

The disturbances to our environment caused by rapid human development since the 1950s have led many researchers and ecologists to dub our current moment “The Anthropocene” — an epoch during which human activity is having massive consequences on the earth’s climate and ecosystems.

As food security and development expert Jagadish Wagle explains, human activity in the Anthropocene has “increased the risks of sudden collapse and irreversible changes”, and led us to the precipice of nine key planetary boundaries. We are now at risk of causing a massive drop in biodiversity and are far beyond the safe boundary for biochemical flows.

Crossing these planetary boundaries will have dire effects on underprivileged human populations around the globe, but it will also cause massive disturbances to animal life that have existed in a state of relative ecological balance for thousands of years. In particular, human activity will uniquely impact migratory animals, which rely upon a stable climate and semi-consistent landscapes for reproduction, feeding grounds, and better seasonal conditions.

But most folks don’t understand the tender balance between migratory animals and the wider ecosystem. Though it may be hard to imagine, even small changes to farmland and urban areas can have dire consequences for migratory birds, insects, and mammals.

Humands and Animal Migration: bird flying over city

Urban Development and Migratory Birds

Current projections estimate that the human population will be over 10 billion by 2050 and that the bulk of humanity will live in cities and towns. This makes sense, as those who live in urban areas typically have greater access to healthcare, a higher quality of education, and greater economic opportunities. However, urban development can wreak havoc with birds’ migratory patterns, particularly when urban planners create cities from the dust in just a few years and with little concern for the local ecology.

Light pollution is one major source of disruption for migratory birds. That’s because migratory birds use changes in light to time their migratory patterns, but light pollution from nearby urban areas and unseasonably warm winter months can confuse birds and cause them to migrate later than is optimal. This has a knock-on effect on migratory birds’ ability to reproduce, as flocks that migrate late may find stiffer competition for food and mates.

While it sounds bizarre, buildings and urban skyscrapers themselves present a real danger to migratory birds. Researchers estimate that, in the US alone, at least 100 million birds die due to collisions with skyscrapers every year. This is particularly true for migratory birds, who are attracted to light and may lead their flocks into dangerous urban areas where fatal collisions are far more likely. Homeowners and urban developers can reduce the chance of fatal collisions by using decals and bird tape that break up mirror-like reflections. Urban architects can also do their bit by using acid-etched glass which reduces opacity and ensures that birds see the building, rather than a reflection.

Agriculture and Migratory Insects

When we hear the term “migration”, we usually think of geese flying overhead or herds of bison crossing the Great Plains. But much smaller animals also make monumental journeys several times a year in search of food, appropriate weather, and reproduction.

One such migratory insect is the monarch butterfly. Monarch butterflies are a favorite amongst school teachers and researchers due to their distinctive orange wings and the critical role they play in pollinating their local ecosystem. Monarch butterflies also migrate 3,000 miles every year between the northeast of America and Canada down to the southwest of Mexico.

But the monarch butterfly is in major decline due to the removal of milkweed from farms and fields across much of the US. This is an issue, as monarch butterflies’ larvae are hatched on milkweed plants and exclusively eat the plant until they transform into butterflies. Additionally, monarch butterflies may use milkweed as a form of navigation, as their migratory patterns likely follow the food source in both the winter and warmer months.

Overfertilization removes milkweed from farms and open areas and causes major disruptions to monarchs’ migratory patterns. In turn, this reduces the pollination of plants across the US and Mexico and causes a significant drop in local biodiversity. While farmers do need to protect their crops from pests, overfertilization risks wiping out key pollinators and creating knock-on effects on larger ecosystems. Instead, agricultural researchers and farmers should work together to undertake more sustainable development models which create a synergistic relationship between crop production and insect migration patterns.

Domestic Pets and Wild Animals

Every city park, skyscraper, or bus route was once a wild space complete with its own finely balanced food chain. When humans erect urban spaces, we might assume that larger animals like falcons and deer are omitted from plans and, therefore, are unable to find enough food to live in our cities. However, recent data shows that urban beasts are adapting to urban areas and surviving amongst our metros and promenades.

But for migratory animals, urban areas present a unique threat in the form of domestic pets. While humans might snuggle up to their free-roaming cats and pedigree-caliber dogs at night, our pets are a menace to wildlife and greatly reduce biodiversity amongst the wild animals that are tentatively returning to urban spaces. In the US alone, researchers estimate that free-ranging domestic cats kill 1.3-4.0 billion birds and 6.3-22.3 billion mammals every year.

Of course, individuals can always do their bit to reduce the killing of migratory animals by domestic pets. People can start by keeping cats indoors and always observe trail etiquette when walking dogs to ensure that migratory patterns of wild animals are not disrupted by pets. This is particularly important during migratory seasons when dog owners must pay particular attention to park rules that give larger animals like deer the ability to safely migrate through urban green spaces.

Final Thoughts around Humans and Animal Migration

Migratory animals play a vital role in sustaining our ecosystem. Pollinators like monarch butterflies help flora and flora spread across continents, and larger animals like birds and deer are key to supporting healthy food chains. In recent years, data has revealed the cost of human development, and researchers have found credible evidence to suggest that billions of wild animals are being wiped out by human activity. We clearly need further thought and investment to create a more habitable planet for all animals during the Anthropocene.

About the Author

Amanda Winstead is a writer focusing on many topics including technology and digital marketing. Along with writing she enjoys traveling, reading, working out, and going to concerts. If you want to follow her writing journey, or even just say hi you can find her on Twitter.