February 8, 2017 Environmental Issues Written by Greentumble
The main threats to wildlife migrations
Commuting to work is a daily nightmare for

most of us either due to the long distances the need to be travelled, the absence of good public transport links or simply congestion. Some have it worse than others: for example, in the UK the average commute is about an hour while in the US just under 30 minutes [1,2]. But if you thought that humans have it bad, just think of the distances many animals need to travel to find shelter, food or just a friendlier environment.

Animal migrations are a fascinating phenomenon showcasing how our planet’s ecosystems are connected. The bar-tailed Godwit is known as the bird with one of the longest non-stop flights as it breeds in Alaska and then migrates south to Australia and New Zealand completing a non-stop flight of over 9 days over the Pacific Ocean [3].

But it is not just birds that migrate, it is all sorts of animals such as fish, crustaceans, amphibians, reptiles, insects or mammals.

For example, dragonflies are capable of long-distance migrations, of up to 14,000 to 18,000 kilometres following a route that spanned from India to the Maldives, the Seychelles, Mozambique, Uganda and back again. This epic migration spans across four generations of dragonflies, with each generation playing its part in the journey like a relay race [4].

But increasingly these amazing journeys that species make from across the globe and depend on for their survival are being compromised. Indeed, several threats to wildlife migrations have been identified which the examples below help to illustrate.

Disappearing habitats

A very clear concern is that habitat loss and destruction means that species returning to a location can no longer find shelter or food. This is particularly important for species seeking to mate in that location.

For example, Monarch butterflies fly up to 3,000 miles south from their home in the Rocky Mountains to spend the cold winter months in the warmer climates of Mexico and Southern California. The journey spans across several generations are the butterflies only live for three months, and yet they can still return to the same tress their ancestors inhabited the previous winter.

But illegal deforestation and logging in Mexico is compromising this migration of butterflies and has led to a sharp drop in their numbers. What is more butterflies’ journey is severely impacted by the widespread use of herbicides across the US which has led to the elimination of the milkweed, a source of food for the butterflies [4,5].

Increasing human wildlife conflicts

The migration of wildebeest and zebra from Tanzania’s Serengeti national park into Kenya’s Masai Mara reserve is a very unique event as more than 2 million herbivores, such as zebras, gazelles and wildebeests, cross East Africa’s plains at the beginning of the dry season in June.

Unfortunately, meat poaching to supply local food markets is disrupting this journey while the use of land for agriculture is fragmenting their route. Migratory corridors and dispersal areas usually cross human-dominated landscapes where land use practices are becoming increasingly incompatible with wildlife [6].

Even climate change…

European songbirds such as barn swallows or robins, which spend their summers in the temperate regions of Europe before heading to South African wintering grounds some 6,000 miles away, are now also facing an increasing number of challenges.

Not only to they have to cross the Sahara Desert, risking starvation and exhaustion, but climate change is confusing birds about when to migrate, with some species leaving too early or too late, and industrial agriculture is reducing food supplies for many birds. What is more, illegal trapping of songbirds is also on the rise [5].



[1] https://project.wnyc.org/commute-times-us/embed.html#5.00/42.000/-89.500
[2] https://goo.gl/99x0lO
[3] http://www.nature.com/scitable/knowledge/library/animal-migration-13259533
[4] https://goo.gl/IYEQIY
[5] http://www.takepart.com/article/2015/03/31/migration-and-threats