A new study, published in NEcology & Evolution ature, found that overfishing was still a problem on the little-studied borders of a marine protected area (MPA)

Marine Protected Areas are one of the key measures proposed by various countries when it comes to protecting the biodiversity of the ocean.

Climate actions taken at the G7 and expected at COP26 include the creation of more protected areas of forests and oceans, in the hope that overfishing will decrease and fish stocks can replace themselves – while the coral reefs of the world are also protected.

So how well do MPAs really work?

The internal area of ​​an MPA is accepted as a stronghold for fish stocks and biodiversity, as ocean life has a chance to exist without human interruption. Some are pushing for nature to have legal rights, as opposed to passive protection. However, when it comes to the point where an MPA touches an open fishing area, the protection dynamic that takes place at the borders is less well understood.

A study by Tel Aviv University reveals ecological damage to many MPAs around the world, via a “side effect”.

What is the edge effect?

Liz Clift, environmental writer, said: “In ecology, side effect refers to changes in a population or community along the boundaries of a habitat. A clear example of this is when an agricultural field meets a forest.

In ecology, the side effect happens to habitats that are adjacent to an area – normally on land. This means that species living at the edges of their habitats are more exposed to threats of extinction. The edge effect could also refer to a fragmented habitat, whose shares overlap with totally different environments that impact the biodiversity of all those who share a border.

MPAs have a 60% reduction via the edge effect

The edge effect observed by scientists is a strong reduction of 60% of the fish population living near the protected area, up to a distance of 1 to 1.5 km. This effect actually decreases the size of the MPA, created by human pressures – which are mainly due to overfishing, right at the border.

The team found that 40% of non-harvest MPAs, in which fishing is completely illegal, are less than one square kilometer. This means that the whole area is diminished by an edge effect, which means that the protection theoretically given by the area can be canceled.

In fact, 64% of all MPAs banned from fishing in the world are less than 10 square kilometers in area, further suggesting that they only hold 45-56% of the population size they should. .

Essentially, the edge effect means that the protected areas of the ocean are not doing what they should be doing.

The side effect “has not yet been studied in MPAs”

“When I saw the results, I immediately understood that we were looking at a side effect model,” said Sarah Ohayon, a doctoral student in the lab of Professor Yoni Belmaker, School of Zoology, George Faculty of Life Sciences. S. Wise.

“Side effect is a well-studied phenomenon in terrestrial protected areas, but surprisingly, it has not yet been empirically studied in MPAs. This phenomenon occurs when there are human disturbances and pressures around the MPA, such as hunting / fishing, noise or light pollution that reduce the size of natural populations within MPAs near their borders.

How to solve the problem of the edge effect?

Buffer zones.

Well-applied MPAs have a weaker border effect, and those with buffer zones have zero border effect, meaning that biodiversity is well protected.

Ohayon added: “These results are encouraging, as they mean that by establishing buffer zones, managing fishing activity around MPAs and improving enforcement, we can increase the efficiency of existing MPAs and most likely also increase the benefits they can bring through fish overflow.

“When planning new MPAs, in addition to establishing regulated buffer zones, we recommend that non-harvest MPAs targeted for protection be at least 10 km away.² and as round as possible. These measures will reduce the edge effect in MPAs.

Read the full review article here.